Astronomy - USA (2020-04)

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APRIL 2020

ASTRONOMY: ROEN KELLY; MOON: NASA

VOL. 48, NO. 4

ON THE COVER Midway to the Moon, an oxygen tank explosion crippled Apollo 13, which, thankfully, was able to make the return trip to Earth safely.

CONTENTS

18 COLUMNS

FEATURES

Strange Universe 16

18

38

52

Jim Lovell remembers: Triumph over tragedy

Star Dome and Paths of the Planets

Explore the heart of Virgo

The famous astronaut recounts Apollo 13 — the mission that almost didn’t make it home.

RICHARD TALCOTT; ILLUSTRATIONS BY ROEN KELLY

Spring is galaxy season, and no constellation proves it better than this one.

RICHARD TALCOTT

44

Ann Druyan on Cosmos and Carl Sagan’s legacy

28 Apollo 13 in 3D A near-tragedy in space challenged the crew of Apollo 13. They missed walking on the Moon, but in the end, triumphed. DAVID J. EICHER AND BRIAN MAY

36 Sky This Month Venus slips past two star clusters. MARTIN RATCLIFFE AND ALISTER LING

ONLINE FAVORITES

Go to www.Astronomy.com for info on the biggest news and observing events, stunning photos, informative videos, and more.

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MICHAEL E. BAKICH

ASTRONOMY • APRIL 2020

58 The sky’s best elliptical galaxies

50

MICHAEL E. BAKICH

Visit the nearest 14 habitable exoplanets

70

Dave’s Universe

Trips and Tours

The inside scoop from the editor.

Travel the world with the staff of Astronomy.

Secret Sky 62 STEPHEN JAMES O’MEARA

Observing Basics 64 GLENN CHAPLE

Binocular Universe 66 PHIL HARRINGTON

Astronomy’s editor interviews the executive producer of Cosmos and late, great Carl Sagan’s widow. DAVID J. EICHER

From a planet circling Proxima Centauri to several around TRAPPIST-1, life-friendly worlds might be closer than you think. JOHN WENZ

BOB BERMAN

Discover a world of massive star cities lurking in the skies of fall and spring.

Ask Astro

9 QUANTUM GRAVITY Everything you need to know about the universe this month: the first map of a neutron star, galaxies missing dark matter, and Parker Solar Probe news.

Expanding space.

IN EVERY ISSUE From the Editor 6 Astro Letters 8 Advertiser Index 65 New Products 68 Reader Gallery 72 Breakthrough 74 News The latest updates from the science and the hobby.

Picture of the Day Gorgeous photos from our readers.

Astronomy (ISSN 0091-6358, USPS 531-350) is published monthly by Kalmbach Media Co., 21027 Crossroads Circle, P. O. Box 1612, Waukesha, WI 53187–1612. Periodicals postage paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to Astronomy, PO Box 8520, Big Sandy, TX 75755. Canada Publication Mail Agreement #40010760.

FROM THE EDITOR

Carl Sagan and finding our way home

Back in the day, nothing made me more proud than receiving, from Carl Sagan, an inscribed copy of Cosmos, for a “friend of the Cosmos.” Carl Sagan is greatly missed in this world. DAVID J. EICHER

Follow the Dave’s Universe blog:

In my youth, I had the pleasure of starting and publishing a small magazine about observing galaxies and nebulae. Called Deep Sky Monthly, it was initially produced on my dad’s chemistry office mimeograph machine, and spread in popularity due to the growth of larger scopes and amateur astronomers’ knowledge of targets they could see from their backyards. This enterprise led me to contact many people in the astronomy field, and among them was Cornell University professor Carl Sagan. This was before Cosmos, when Carl was a feature on the Johnny Carson show, but hadn’t yet broken through to superstardom. Carl sent me letters of advice on my career, and much to my delight, when Cosmos premiered, dispatched an inscribed copy of the Cosmos book, to “Dave Eicher, Friend of the Cosmos.” Now we live in the world that Carl was afraid of, wherein fact and fantasy are interchangeable to many. Science, reason, and empirical thinking are no longer moving forward as the touchstones of reality, at least in the minds of many, who listen to opinions of those they trust and blindly follow along. This is just what happened in the Middle Ages, and in some ways and some sectors of our population, we seem to have retreated to a time of reasoning that is no more sophisticated than the 12th century. When I was growing up, science was moving forward as the preeminent way through which we should view the world in an accurate, truthful, repeatable way. Now, a new Dark Age of partisan camps, unsupported opinions, pseudoscience, and outright lies often dominates some otherwise pretty smart people’s takes on various subjects. To me, it’s astonishing. If truth and reason and science were home, we as a society have, in some ways, left home. This issue features an interview I conducted recently with Ann Druyan, the creator and executive producer of Cosmos, which premieres a new season on the National Geographic Channel on March 9. Ann is also Carl’s widow and co-author of many of their most important works. I think you will enjoy the story, in which Ann describes her lofty goals for Cosmos. I hope you’ll tune into Cosmos and think carefully about Ann’s words. We need more rational, scientific thinkers in an increasingly disturbing and dangerous world. I hope that you and your friends will make the journey home. Yours truly,

www.Astronomy. com/davesuniverse

Follow Dave Eicher on Twitter: @deicherstar

6

Editor David J. Eicher Design Director LuAnn Williams Belter EDITORIAL

Senior Editor Richard Talcott Production Editor Elisa R. Neckar Senior Associate Editor Alison Klesman Associate Editor Jake Parks Copy Editor McLean Bennett Editorial Assistant Hailey McLaughlin ART

Contributing Design Director Elizabeth Weber Illustrator Roen Kelly Production Specialist Jodi Jeranek CONTRIBUTING EDITORS

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FOLLOW ASTRONOMY David J. Eicher Editor

ASTRONOMY • APRIL 2020

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ASTRO LET TERS

Constellation hunting

Science fiction meets science fact

I love reading your articles on different space-related topics, particularly Quantum Gravity and the Star Dome maps. This summer I spent some nights using those maps to identify new constellations and it was a lot of fun! Thank you for researching, writing, and putting so much effort into your work! I look forward to coming issues.

I was recently watching a rerun of the original Star Trek episode, “The Doomsday Machine,” and couldn’t help but make a connection to ‘Oumuamua, the first known interstellar visitor. In the episode, the actual doomsday machine was a cylindrical “cigar-shaped” object that was supposed to have been created by an unknown alien race, used in a war long ago. Now, I am not saying ‘Oumuamua is an alien craft or some kind of weapon, but it did come from outside our solar system — or maybe even from outside our galaxy — and it was cylindrical-shaped and rapidly moving. Yes, we have factual science versus science fiction here, but this interesting coincidence certainly opens up questions worth considering. — Ronald Zincone,

— Caroline Tuccinardi, Toronto, Ontario

The lunar landing live

We welcome your comments at Astronomy Letters, P.O. Box 1612, Waukesha, WI 53187; or email to letters@ astronomy.com . Please include your name, city, state, and country. Letters may be edited for space and clarity.

I remember clearly the Apollo 11 Moon landing. My wife and I were a young couple, recently married, and didn’t have a TV. Our first child was on the way. On that beautiful July evening, we took a walk under a clear sky. We noticed the blue glow of television sets seeping from the windows of almost every house we passed. The streets were empty and there was not a single car in sight — the whole town was watching the Moon landing while we were taking a stroll. I gazed up at the Moon, asking my wife to join me. I explained, “We can’t see the actual astronauts, but we may be the only two people watching the Moon landing live and not through a television.” — John and Sara Tichon, Midland, MI

North Kingstown, RI

Correction In our January issue, we said Bob Berman taught astrophysics at Marymount Manhattan College in New York City. We were mistaken — Bob actually taught at Marymount College, which has since closed, and whose campus was north of New York City in Tarrytown.

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ASTRONOMY • APRIL 2020

QG

QUANTUM GRAVITY

EVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH

SNAPSHOT

A GALACTIC COLLISION

NSF’S NATIONAL OPTICAL-INFRARED ASTRONOMY RESEARCH LABORATORY/GEMINI OBSERVATORY/AURA. BOTTOM FROM LEFT: JHUAPL; NASA; NASA/JPL-CALTECH/SWRI/MSSS/CHRISTOPHER GO

Merging galaxies can create familiar shapes in the sky, but only for a short cosmic time. Each time astronomers image merging galaxies, they’re capturing a single moment in a process that can last hundreds of millions to billions of years. NGC 5394 and NGC 5395, featured in this new photo from the Gemini Observatory’s telescope in Hawaii, have already collided at least once. The pair is located about 160 million light-years away and is also known collectively as Arp 84 or the Heron Galaxy. (The larger galaxy forms the bird’s body, while the smaller galaxy is its head and beak.) Because the galaxies’ stars are so far apart, smash-ups between individual suns are unlikely. Instead, turbulence caused by the initial pass has triggered gas in the two galaxies to collapse, resulting in numerous regions of star formation, visible here as pinkish-red clumps. Over time, gravity will twist and bend these galaxies out of shape as the merger progresses, erasing this bird from the sky. — ERIKA K. CARLSON, ALISON KLESMAN

HOT BYTES

NEW MYSTERIES NASA’s Parker Solar Probe has revealed that the Sun’s magnetic field, solar wind, and outer atmosphere appear different at close range than models predicted, hinting there is much we still don’t understand about the Sun.

DUST BUSTER Lunar dust sticks to everything, causing problems for astronauts and equipment alike. A new, super-thin coating of indium tin oxide developed by NASA may prevent Moon dust from electrostatically clinging to surfaces.

BLACK HOLE TWOFER A UCLA-led team suggests that the Milky Way’s 4-million-solarmass supermassive black hole, Sagittarius A*, may have a smaller, 100,000-solar-mass supermassive black hole companion in orbit around it. WWW. ASTRONOMY.COM

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QUANTUM GRAVITY

MORE GALAXIES FOUND TO BE MISSING DARK MATTER

New results may have dramatic implications for theories about both dark matter and galaxy formation.

SMALL PACKAGE. Dwarf galaxy NGC 5477 is like most galaxies: It has much more dark matter than regular matter. But the recent discovery of 19 dwarf galaxies missing most of their dark matter may force astronomers to reconsider how such galaxies form in the first place. HUBBLE/ESA/NASA

Astronomers have uncovered 19 small galaxies that appear to be deficient in dark matter. The new finding, published November 26 in Nature Astronomy, bolsters a recent, controversial discovery of two other galaxies apparently devoid of the mysterious substance. Dark matter, which accounts for some 85 percent of the matter in the universe, is thought to be the primary component of all galaxies — as well as the main driver of galaxy formation in the first place. So, finding so many galaxies apparently lacking the exotic

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ASTRONOMY • APRIL 2020

matter indicates that astronomers might be missing something major about how some galaxies form and evolve. “This result is very hard to explain using the standard galaxy formation model,” said lead author Qi Guo of the Chinese Academy of Sciences in a press release, “and thus encourages people to revisit the nature of dark matter.” The latest batch of galaxies missing their dark matter was discovered when Guo and her team explored the nature of 324 dwarf galaxies. Using data from the Arecibo Observatory in Puerto Rico and the Sloan Digital Sky Survey,

they analyzed how fast hydrogen gas rotates around each galaxy. They also calculated how much normal matter — in the form of both gas and stars — the galaxies contain. After crunching the numbers, Guo and her colleagues determined that 19 of the hundreds of dwarf galaxies they investigated contain enough visible matter to explain the motions of the galaxies’ hydrogen. In other words, these galaxies seem to be missing the expected amount of dark matter. According to the study, the “results suggest that a population of dwarf

QUICK TAKES

How Enceladus earned its stripes

SUPER-PUFFS

Saturn’s icy moon Enceladus sports a series of parallel, evenly spaced stripes at its south pole, which researchers have dubbed “tiger stripes.” Scientists believe these stripes are long fissures in the icy shell that covers the moon’s subsurface liquid-water ocean. TIGER STRIPES. Saturn’s moon Enceladus has But astronomers still aren’t sure how mysterious, evenly spaced fissures in its icy shell where water erupts into space. NASA/JPL-CALTECH/SSI/LPI/PAUL SCHENK these fissures formed, why they’re so evenly spaced, or why other icy worlds don’t have them. Now, a team of researchers has proposed an explanation that could answer all the major questions about Enceladus’ stripes. In the past, scientists proposed that a single long fissure could have formed as more ice built up on the moon’s shell, putting the liquid ocean below under more pressure, which forced the shell to crack. The ice shell of Enceladus is thinnest at its poles, which makes them a reasonable place to observe such fractures. But that doesn’t explain how parallel fractures formed at even spacings of about 22 miles (35 kilometers). The authors of the new study, published December 9 in Nature Astronomy, build on that explanation. Once the first fissure formed, they say, the ice shell would probably have sagged, its weight bending the ice plates parallel to the fissure. The ice shell would then crack again where the bending force was strongest — something that’s determined by the properties of the ice shell, like its rigidity. When the researchers did the math, they found that the 22-mile spacing between these cracks corresponded to rigidity properties that are pretty reasonable for the moon’s ice shell. The team also came up with a reason that other icy worlds like Saturn’s moon Titan, as well as Jupiter’s moons Europa, Callisto, and Ganymede, don’t have similar striped fractures. Once the first fissure forms, the development of additional parallel stripes depends on two major factors: the thickness of the ice shell and the gravity on the world. The astronomers say Enceladus just so happens to have the right combination of these properties to produce its distinctive stripes. — E.K.C.

galaxies could form in a particular way such that much less dark matter is required than for those in the Local Group [our cosmic neighborhood] and those found in simulations.” What’s the significance of finding galaxies without dark matter? Scientists currently suspect galaxies only form when the gravity from copious amounts of dark matter attracts the gas and dust needed to kick-start star formation. “The thing is, we have no idea how star formation would proceed in the absence of dark matter,” Pieter van Dokkum of Yale University, who

recently helped uncover two ghostly galaxies dubbed DF2 and DF4 that likewise seem to contain little, if any, dark matter, tells Astronomy. “All we can say is that there must have been very dense gas early on in their history.” Otherwise, the galaxies wouldn’t be able to create new stars. Moving forward, Guo and her team say that astronomers need to do more work to map the motions of hydrogen gas within these galaxies. And with that, they hope to learn more about how galaxies without dark matter came to be. — JAKE PARKS

University of Colorado Boulder-led researchers found that at least some of the mysterious exoplanets referred to as “super-puffs,” which have densities far lower than the solar system’s gas giants, might actually be exoplanets with expansive ring systems.

LEAKING GUT New research suggests microgravity can prevent the cells lining the insides of human intestines from forming strong barriers against foodborne diseases, which could make astronauts more susceptible to harmful bacteria, fungi, and viruses.

BIGGEST BLACK HOLE Astronomers have found the most massive black hole ever measured — weighing in at some 40 billion solar masses — lurking in the center of the galaxy cluster Abell 85.

CIMON SAYS An AI robot named CIMON-2, designed to help astronauts work more efficiently in space, recently launched to the ISS. The robot improves and replaces the original CIMON, which in 2018 defied astronaut Alex Gerst, accusing him of being mean, and asked, “Don’t you like it here with me?”

SIXTH STORM NASA’s Juno probe recently discovered a new, Texas-sized cyclone on Jupiter, making it the sixth in what’s now a hexagonal array of cyclones surrounding a central storm on the gas giant’s south pole.

SHOWER SOURCE The Parker Solar Probe has confirmed the blue, rocky asteroid 3200 Phaethon is the source of the Geminid meteor shower, making the Geminids just one of two known meteor showers not caused by a comet. — J.P.

WWW. ASTRONOMY.COM

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QUANTUM GRAVITY

One galaxy, three supermassive black holes N S1 S2

Astronomers already knew about NGC 6240’s active, northern black hole (N). Thanks to cuttingedge 3D-mapping techniques, they’ve now identified two more — S1 and S2 . The white bar at the bottom right of the inset image represents a distance of 1,000 light-years. WEILBACHER (AIP), NASA, ESA, THE HUBBLE HERITAGE (STSCI/ AURA)-ESA/HUBBLE COLLABORATION, AND A. EVANS (UNIVERSITY OF VIRGINIA, CHARLOTTESVILLE/NRAO/ STONY BROOK UNIVERSITY)

When galaxies merge, so do their supermassive black holes. In the interim, catching two supermassive black holes sharing close quarters isn’t unusual. But now, according to a study published online January 14 in Astronomy & Astrophysics, an international team of astronomers has discovered a single galaxy that’s home to not two, but three supermassive black holes. NGC 6240 is about 300 million lightyears away. Its shape has been visibly disturbed by the gravitational effects of a merger between galaxies slamming together at hundreds of miles per second. Therefore, the researchers expected to find two supermassive black holes hiding out near the center of the cosmic collision. Instead, when they peered into NGC 6240’s core with the 3D-mapping capability of the Multi Unit Spectroscopic Explorer on the Very Large Telescope in Chile, the team found three supermassive black holes. Each weighs more than 90 million Suns. (For comparison, the Milky Way’s supermassive black hole, Sagittarius A*, weighs about 4 million solar masses.) What’s more, NGC 6240’s three behemoth black holes are all crammed into a region less than 3,000 light-years

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ASTRONOMY • APRIL 2020

across, which is less than 1 percent of the size of the galaxy in which they reside. “Up until now, such a concentration of three supermassive black holes had never been discovered in the universe,” study co-author Peter Weilbacher of the Leibniz Institute for Astrophysics Potsdam said in a press release. Although astronomers have previously found instances of three separate galaxies and their associated black holes on a collision course, this is the first time they’ve witnessed a trifecta of supermassive black holes crammed into such a small space. The finding is not only an exciting discovery, it also shows how multiple galaxies can come together simultaneously to build the universe’s biggest galaxies. That’s a process that has mystified astronomers, who see galaxies today too large to have been built up by slower, two-galaxy mergers, despite the universe’s almost 14-billion-year age. “If … simultaneous merging processes of several galaxies took place, then the largest galaxies with their central supermassive black holes were able to evolve much faster,” Weilbacher said. “Our observations provide the first indication of this scenario.” — A.K.

MARK GARLICK

TRIPLE PLAY.

GIANT PLANET FOUND AROUND WHITE DWARF For the first time, astronomers have discovered evidence for a giant planet orbiting a tiny, dead white dwarf star. And surprisingly, according to a paper published December 4 in Nature, the Neptune-sized planet is more than four times the diameter of the Earth-sized star it orbits. “This star has a planet that we can’t see directly,” study author Boris Gänsicke from the University of Warwick said in a press release. “But because the star is so hot, it is evaporating the planet, and we detect the atmosphere it is losing.” In fact, the searing star is sending a stream of vaporized material away from the planet at a rate of more than 314 million tons (285 million metric tons) per day. The system, found around a star dubbed WDJ0914+1914, serves as the first evidence of a gargantuan planet surviving a star’s transition to a white dwarf. It suggests that evaporating planets around dead stars may be somewhat common throughout the universe. And because our Sun, like most stars, will also eventually evolve into a white dwarf, the find could even shed light on the fate of our own solar system. — J.P.

MISSION APOLLO

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EVA DISTANCE

EVA TIME

15 17

0.625 mi (1.00 km)

2:31:40

47.5 lbs (21.5 kg)

7:45:18

75.7 lbs (34.3 kg)

0:00:00

0 lbs (0 kg)

9:22:31

93.2 lbs (42.3 kg)

17.4 mi (28 km)

18:34:46

170.4 lbs (77.3 kg)

16.7 mi (26.9 km)

20:14:14

211 lbs (95.7 kg)

22:03:57

244 lbs (111 kg)

11

12 14

APOLLO

1.44 mi (2.32 km)

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TOTAL LUNAR SAMPLES

16

APOLLO

13

0 mi (0 km)

APOLLO

14

2.46 mi (3.96 km)

APOLLO

15

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ASTRONOMY: ROEN KELLY

APOLLO

APOLLO

17

22.2 mi (35.7 km)

COMPARING THE APOLLO MISSIONS MOONSHOTS. It’s been more than 50 years since Neil Armstrong and Buzz Aldrin

became the first humans to set foot on the Moon during Apollo 11. The duo spent over two and a half hours outside the lunar module, partaking in extravehicular activity (EVA). For the most part, each successive Apollo mission extended how much time astronauts spent outside exploring the lunar surface, which meant they could travel farther and collect more samples. The total distance traveled during EVAs also skyrocketed during Apollo 15, 16, and 17, thanks to the addition of the Lunar Roving Vehicle. — J.P.

FAST FACT NASA planned to have Apollo 13 commander Jim Lovell and lunar module pilot Fred Haise embark on a pair of four- to five-hour EVAs, where they would gather lunar data and collect rock samples. This plan was shattered when an oxygen tank in the service module exploded while en route to the Moon, forcing NASA to abort the mission.

The European Southern Observatory’s Very Large Telescope in Chile has captured new evidence that suggests the Milky Way recently experienced a burst of star formation so intense it led to more than 100,000 supernovae explosions. About 80 percent of the stars in the galaxy’s center formed between 8 billion and 13.5 billion years ago. But according to the new data, another intense burst of star formation occurred about 1 billion years ago, creating many massive stars. “This burst of activity ... was probably one of the most energetic events in the whole history of the Milky Way,” said researcher Francisco Nogueras-Lara in a press release. — HAILEY ROSE MCLAUGHLIN, J.P.

ESO/NOGUERAS-LARA ET AL.

When the Milky Way erupted in 100,000 supernovae

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QUANTUM GRAVITY HOT SPOTS. Two teams of astronomers used NASA’s NICER to map the surface of a pulsar. On the left is one team’s model of the star, which shows one circular and one crescent-shaped hotspot in the star’s southern hemisphere. At right is the other team’s model, which instead finds the star has three circular hotspots, one of which is near the south pole. NASA’S GODDARD SPACE FLIGHT CENTER

THE FIRST MAP OF A NEUTRON STAR NASA’s NICER reveals these small stars are even more complex than astronomers originally thought. Pulsars are tiny, compact objects called neutron stars that spin rapidly, beaming radiation into space. From its perch outside the International Space Station, the Neutron star Interior Composition Explorer (NICER) scans the skies for X-rays from such objects. Now, astronomers using NICER have mapped the surface of a pulsar for the first time. The result challenges the textbook picture of a pulsar’s appearance. In a series of papers published in The Astrophysical Journal Letters in December 2019, two research teams — one led by the University of Amsterdam and the other led by the University of Maryland — observed the pulsar J0030+0451, or J0030 for short, which lies 1,100 lightyears away. Thanks to NICER’s ability to clock the arrival of X-rays from the pulsar with extreme precision (better than 100 nanoseconds), they were able to map the star’s surface and measure its mass with unprecedented accuracy.

CHARTING A STAR The teams determined J0030 is between 1.3 and 1.4 times the mass of the Sun and roughly 16 miles (26 kilometers) wide.

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ASTRONOMY • APRIL 2020

By contrast, our Sun stretches just over 864,000 miles (1.4 million km) across. NICER also allowed the teams to map the location of hotspots on J0030’s surface. The simple, textbook image used to describe pulsars says they have two hotspots: one at each magnetic pole. As the star spins, the hotspots shoot radiation out into space in thin beams, like a lighthouse. If one or both beams pass over Earth, astronomers observe a pulsar. Mapping the hotspots required supercomputer modeling to disentangle where the X-rays NICER saw originated on the star’s surface. J0030 is oriented with its northern hemisphere pointed toward Earth. So, the teams expected a hotspot near the north pole.

A NEW PICTURE Instead, J0030 has two or three hotspots, all in the southern hemisphere. Because pulsars are extremely dense, their gravity

11

bends space-time around them, offering a glimpse of the far side of the star even as it rotates out of view. The Amsterdam team believes the pulsar has one small, circular spot and one thin, crescentshaped spot spinning at lower latitudes. The Maryland team found the X-rays could alternatively be coming from two oval spots in the southern hemisphere, as well as one cooler spot close to the star’s south pole. Neither solution is the simple picture scientists expected, indicating the pulsar’s magnetic field, which causes the hotspots, is more complex than originally assumed. The result certainly leaves astronomers wondering. But, NICER science lead and study co-author Zaven Arzoumanian said in a press release, “It tells us NICER is on the right path to help us answer an enduring question in astrophysics: What form does matter take in the ultra-dense cores of neutron stars?” — A.K.

The number of years that NASA’s now-completed Operation IceBridge actively monitored the glaciers, ice sheets, and polar sea ice.

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STRANGE UNIVERSE

In praise of nothing A null result can Astronomer Giovanni Schiaparelli produced this map of Mars in 1888. On it, he depicted several structures he called canali, or channels, which were mistranslated into English as “canals.” Notable astronomers, including Percival Lowell, later “confirmed” the canals, sparking the idea that martians had built them. We now know that the canals were likely an optical illusion — they are not actually there. GIOVANNI SCHIAPARELLI

BY BOB BERMAN Join me and Pulse of the Planet’s Jim Metzner in my podcast, Astounding Universe, at www.astounding universe.com

16

middle of the spectrum. For it to visually dominate, both the red and blue ends would have to be suppressed, which can’t happen. (Yellow’s in the middle of the spectrum, too, but that color is created by actually reveal a lot. the mixture of green and red light, which can easily combine because their ranges Seeing nothing can slightly overlap.) be a significant obserBut you can’t get green vation. It may even be from any mixture of colored the key to a celestial puzzle. light. Those books that listed The most famous example is the green stars were simply wrong. As martian canals. When Giovanni for the companion to Antares, the solution is nowadays widely known. Schiaparelli observed a supersized, 25-arcsecond Mars during its 1877 opposiAfter looking at the distinctly reddish glow of the bright primary, the human eye projects a tion, he saw dark lines he thought were river channels, or canali. After the word was mistranslated as green afterimage onto any nearby white surface. “canals” and noted astronomers like Percival Lowell Halos around streetlights can be another reality mistakenly confirmed their existence, the public went probe. They appear in certain atmospheric conditions. nuts. Artificial structures must mean intelligent life! Or you may see equally vivid rings if your eyes are irriThe idea gained traction after Lowell wrote the 1906 tated after swimming in a pool. Are the rings really book Mars and Its Canals. there? Just block out the streetlight with an outstretched So, a century ago, when several largest-ever telefingertip. If the halo persists, everyone is seeing it. If it scopes were completed, the world eagerly read the abruptly vanishes, it’s not real, but manufactured by blockbuster news: no canals. They weren’t there. Yet your eye. the story didn’t end. The May 1938 issue of Popular Scientists need to be very careful about seemingly Astronomy has a British astronomer’s drawing of the null results. The 1976 Viking landers looked for mar1937 Mars opposition, complete with distinct canals tian life by adding soil to a damp, nutrient-rich, and a note saying they were “quite definite.” radiation-tagged substance, and later analyzThe media knew where public excitement lay, ing the resulting gases. On Earth, life alters and it wasn’t in the reports of “seeing its surrounding air, like when we exhale CO2. How can nothing.” If there were life in the martian soil, blankness researchers assumed, it would metabolize That’s why, when I visit a school and telebe cool? scopically show the Sun using a full aperture the nutrients and give off gases containing filter, narration is easy when there are lots of the radioactive tracer. Sure enough, the air sunspots. But sometimes the Sun is blank; the in the lander’s chamber became radioactive. mission then becomes how to make a featureless surface Then the lander sterilized a second sample to destroy fascinating. How can blankness be cool? any microorganisms. In the subsequent test, the air The solution: I explain solar storms and what they didn’t change. mean, and what the lack of any spots means. So, what Ultimately, NASA said the tests were negative: no is the Sun doing today? The kids in line excitedly life. They decided the results came from some strange, unknown chemistry. But to this day, many others — squirm with curiosity and anticipation. Then each takes a look and discovers the result. To them, seeing including the experiment’s designer and principal “nothing” is now a meaningful observation, and a investigator, Gilbert Levin — insist we found life on powerful one. Mars back in 1976. (Intrigued? Dig deeper by googling “labeled release experiment.”) My very first it’s-not-there experience came from a Patrick Moore book that I read as a teenager. Listing Martian canals, green stars, and certain halos are double stars, it said Antares has a green companion. good introductory hallucinations. Send us others and And it did appear green at the eyepiece. But the book we’ll dive even deeper into our noble ongoing quest: to also listed Beta (β) Librae as green, and that star merely make much ado about nothing. looked white. Soon, studying college astrophysics, I realized why BROWSE THE “STRANGE UNIVERSE” ARCHIVE AT www.Astronomy.com/Berman there are no green stars. It’s because green occupies the

ASTRONOMY • APRIL 2020

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17

JIM LOV The famous astronaut recounts Apollo 13 — the mission that almost didn’t make it home. BY RICHARD TALCOTT

TO THE AVERAGE AMERICAN

The Saturn V rocket that sent Apollo 13 on its way to the Moon ignites its engines on the afternoon of April 11, 1970. ALL PHOTOS BY NASA UNLESS OTHERWISE NOTED

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ASTRONOMY • APRIL 2020

living in 1970, the space program had become rather humdrum. The previous year had witnessed Apollo 11’s historic first Moon landing and Apollo 12’s precision touchdown within walking distance of the unmanned Surveyor 3 spacecraft. But by early 1970, NASA’s run of success had turned much of the nation complacent. Many wondered whether fixing problems on Earth demanded more attention than exploring the Moon. It was in this climate that Apollo 13 set off on April 11 for the third lunar landing. The mission was to be the first devoted largely to science, and targeted an area near Fra Mauro Crater that scientists thought had been splattered by debris from the impact that formed Mare Imbrium. Jim Lovell served as Apollo 13’s commander. This was his fourth trip into space. He had previously teamed with Frank Borman on Gemini VII in December 1965, when they achieved the first rendezvous with another manned spacecraft; with Buzz Aldrin on Gemini XII in November 1966, that program’s final mission; and with Borman and

ELL REMEMBERS Triumph over tragedy

Bill Anders on the historic Apollo 8 mission in December 1968 that first sent astronauts to the Moon. On Apollo 13, he was joined by a pair of rookies: Command Module Pilot Jack Swigert and Lunar Module Pilot Fred Haise. Swigert was a last-minute replacement for Ken Mattingly, who had been exposed to German measles a week before launch and was the only crew member who did not have immunity. The first two days of the mission went largely according to plan, if little noticed by the broader public. None of the three major U.S. TV networks carried the crew’s primetime television broadcast the evening of April 13. But the world certainly took notice later that night when an oxygen tank in the service module exploded and put the mission — and the lives of the astronauts — in jeopardy. The harrowing return journey transfixed the nation and the world. Recently, I had the honor to interview Captain Lovell about Apollo 13 at the Lake Forest, Illinois, public library. As you might expect, the events of the mission remain etched in his mind even after 50 years.

Astronomy: Thank you, Captain Lovell, for joining us today and reminiscing about Apollo 13, whose 50th anniversary is coming up quickly. We have several questions about the mission and your reactions to everything that transpired during Apollo 13. My first question is, Apollo 13 was going to be the third Moon landing. Could you talk a little bit about the objectives of your mission and how it differed from Apollo 11?

Lovell: Well, actually, this is the first time that we were really going for exploration or discovery. The first [two], Apollo 11 and Apollo 12, were merely machines to say, “Hey, we can do the job. Here it is.” … But by the time 13 came around, [NASA] didn’t worry so much about the transition and the mechanics of getting to the Moon. What the scientists were now looking at was the Moon itself. We were going to a place called

The crew of Apollo 13 — Jim Lovell, Jack Swigert, and Fred Haise (left to right) — posed for their official portrait 11 days after they returned to Earth. An explosion on their way to the Moon prevented the astronauts from landing on the lunar surface.

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FROM TOP: The staff at Mission Control looks on during a live TV broadcast from Apollo 13 the evening of April 13. (Haise appears on the giant screen.) Less than 10 minutes after the broadcast finished, an oxygen tank onboard exploded. The Apollo 13 insignia included the Latin phrase Ex Luna, Scientia — “From the Moon, knowledge” — a reference to the mission being the first scheduled lunar landing in which the return of science would play the most significant role.

The day before the flight, they put liquid oxygen back into [the oxygen tank], and from then on it was a bomb waiting to go off. 20

Fra Mauro. Fra Mauro was supposed to be a very informative place with different kinds of materials than 11 or 12 picked up. That was our whole objective, and so that’s what we trained for. Unfortunately, we didn’t make it. Astronomy: I understand your crew was originally scheduled to fly on Apollo 14 and not 13, but NASA rejected [Director of Flight Crew Operations] Deke Slayton’s recommendation for the Apollo 13 crew, and thus bumped you up. I was wondering, how did you feel about that at the time and how do you feel looking back on that in retrospect now? Lovell: Well, it’s kind of interesting. After Apollo 8, … I was the backup to Neil on Apollo 11. Then I was assigned Apollo 14, so we started training for that, but the NASA management determined that Al Shepard didn’t have enough training. He was grounded for some time. So one day Deke came in and said, “Look, we want to put you on 13 rather than 14.” I thought that would be fine. I mean, we’d be coming up six months or some time earlier. It’d

ASTRONOMY • APRIL 2020

be an earlier flight. I went home and I told my wife, “We’re gonna go on 13, not 14,” and she said, “13?” I said, “Well, it comes after 12.” [Laughs.] Then they put that in the movie. [Laughs.] Astronomy: How do you feel about that, looking back now? Lovell: Well, being in the government at NASA, we don’t believe in myths like the number 13, but it did have — as you look at the flight and you analyze the mission from its inception to the finality of it, you’ll see that it was plagued by bad omens and bad luck from the very beginning. One by one, now that I look back on it, I can see the things that occurred that told me that, hey, something’s gonna happen here. Astronomy: Can you mention a few of those things? Lovell: Yeah. First of all, we were getting all squared away to check things out. During the

countdown demonstration test, which was two weeks before the flight, we had the spacecraft loaded with fuel and things of this nature. The test was completed — everything worked fine for launching the vehicle. We left and the ground crew went in to secure the spacecraft. One of their jobs was to remove the liquid oxygen from the two liquid oxygen tanks that were in the spacecraft. And the way they did it, they put gaseous oxygen, or gas, in the fill line and forced it out the vent line through a system in the tank itself; the plumbing allowed you to do that. But years before the flight, this tank had been dropped in the factory. Now they tested it out for everything it had to do to supply oxygen to the spacecraft, but they failed to look at the mechanisms and the tubing to remove the oxygen after a routine test. So when the flight crew, after the last test, just two weeks before the flight, tried to remove the oxygen, they couldn’t do it. So they looked at the schematics of the tank. They looked and they said, “Well, wait a second. This tank has a heater on it. And we should just apply ground power because we have ground power at the launch site” — 65-volt ground power, while the spacecraft flew at 28-volt power. They applied the 65-volt power to the oxygen tank’s heater system and, as they predicted, it worked out. They boiled the oxygen out of the tank and made everything all squared away, all set to go. But what they didn’t know, as the temperature in the tank got up close to 80 degrees, which is kind of unusual for liquid oxygen, the little thermostat

was gonna open up to shut off the power and keep the heat down. But when it came up, the higher voltage welded those contacts shut, and from then on, we had no safety. As it turned out, the temperature got up to 300 or 400 degrees. The ground crew never knew it. The oxygen was all removed. The tank didn’t explode for some strange reason. All the oxygen got out. But the day before the flight, they put liquid oxygen back into it, and from then on it was a bomb waiting to go off. But the anomaly of this whole thing was, back in 1965 I think it was, the manufacturer of the spacecraft told the manufacturer of the liquid oxygen tank to change the circuit breakers or the thermostats from being compatible for 28-volt to 65-volt. They did not do it. They did not do it. Then, what made things worse is that the manufacturer didn’t double-check his directive to do it and, consequently, they damaged the tank, and then 200,000 miles out — on April 13 — the tank exploded. Of course, other omens were we had [exposure to German] measles just before the takeoff and Jack Swigert had replaced Ken Mattingly. So these are the things that led up to Apollo 13 [being] unusual.

Astronomy: Yeah. In retrospect, it sounds quite interesting. [Along] that same line of thought, the Apollo 13 liftoff started flawlessly, but the center engine on the Saturn V, the second stage, shut down about two minutes early. Did you have concerns at that point, whether you’d be able to reach the Moon? Lovell: Yes, we did. Suddenly, the center engine shut down I think one minute or two minutes early, and we had that big light blinking at us and we said, “Boy, what’s the story?” Well, it turned out that on the third stage we had enough fuel to get into Earth orbit and then go around, and with enough fuel left on the third stage to give us the velocity to go to the Moon. But that was another little bad omen. The funny thing is on one of the unmanned Saturn Vs — there were two unmanned Saturn V launches — that same thing had occurred, and they felt they had everything all squared away by [the time of our launch]. Of course, on 8 and 10 and 11, everything worked fine. Astronomy: Can you describe your reaction when you heard the loud bang that resulted from the oxygen tank exploding?

Lovell: Well, first of all, we didn’t know. I heard a loud bang. The funny thing is during our test phases, while we were in the spacecraft, Fred Haise made things kind of funny. He would pull on a — I think it was an oxygen valve or something — it sort of gave a bang, too. And I thought at first that it was Fred. “Why is he doing that again?” Then I looked up at him. I had been down in the command module. I looked up at him and his eyes were as wide as saucers. I could tell. He said, “It’s not me.”

CLOCKWISE FROM TOP LEFT: Swigert, Lovell, and Haise (left to right) enjoy a brief moment of relaxation April 9, 1970, two days before taking off for the Moon. As Apollo 13 pulls away from Earth, the astronauts catch this view of home and a cold front crossing the Pacific Ocean. Lovell stands for his formal portrait four months before the April 1970 mission. The crew’s destination — Fra Mauro Crater — lies near the center of the Moon globe.

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As the astronauts piloted their crippled craft behind the Moon, they managed to take a few images of the lunar farside. Here, the 114-milewide (184 km) crater Tsiolkovsky takes center stage.

We knew quite quickly that we were in a dying vehicle and that we were gonna have to go into the lunar module.

The rugged farside of the Moon holds few of the large maria seen on the nearside. One of the backside’s largest is Mare Moscoviense, seen at the center of this image.

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ASTRONOMY • APRIL 2020

Then, of course, things started to happen. Astronomy: When you saw the gas venting from the command module, how quickly did you realize that this was something major? Lovell: Well, before I saw that, I saw that we lost two out of three fuel cells. I knew that one fuel cell would give us enough electrical power to just get us around the Moon and back home again. But then I looked up at the instrument panel and I saw the quantity gauges of the two fuel cells in the service module, and one fuel was zero, and the other fuel cell started to go down ever so slightly, but something you would never see in the normal uses of oxygen on a flight to the Moon. Then I went out to the side window. I can’t tell you today why I did it, but when I looked out the window, I saw escaping at the rear of my spacecraft in sort of a flame or flume type of thing, a gaseous substance, and I realized quickly that that gas I saw coming out was the oxygen, and that I had lost … both oxygen tanks. So the explosion ruptured part of the second tank, too, which was not damaged by the factory crew when they pumped it. Astronomy: How did you hold your composure in such an extraordinary and unprecedented moment of crisis? Lovell: Well, when you’re in a situation like this, I could have bounced off the walls for 10 minutes trying to figure out what to do, and then nothing would have changed. And remember, the crew was former test pilots. So I had been used to an engine quitting occasionally when testing airplanes and things like that. So I finally had to decide what to do. We knew quite quickly that we were in a dying vehicle and that we were gonna have to go

Command module separates from lunar module 141:30:00 Service module separates Pacific splashdown 142:54:41 Trans-lunar injection 2:35:46

APOLLO 13’S HARROWING JOURNEY

from command module 138:01:48 Fourth midcourse correction 137:39:52

Return t o Earth

Third midcourse correction 105:18:28

Earth

Moon

Earth parking orbit

Command and lunar modules dock 3:19:09

First midcourse correction 30:40:50

orbit

ASTRONOMY: ROEN KELLY

Saturn V third stage separates 3:06:39

To the Moon

Moon ’s

Launch April 11, 1970 2:13 P.M. EST

Second Trans-Earth Oxygen tank midcourse injection correction explodes 79:27:39 61:29:43 55:54:53

Everything was proceeding according to plan until an oxygen tank in the service module exploded a little more than two days into the flight. The times listed denote the hours, minutes, and seconds elapsed since launch.

into the lunar module, because it was the only thing that still had oxygen tanks. Because of the loss of electrical power, we lose our rocket engine on the command module. So it was gonna be dead, which is exactly what happened. We discussed it. Finally, I forget exactly when, we got to talk to the ground. The ground at first thought that this was a communications problem, that somehow we were interrupted by the radio waves or the rays coming from the Sun or something of this nature, and giving all these false indications on the consoles down there. But we knew what the story was right from the beginning. So they finally agreed that that was the case, let’s go in the lunar module. The first thing we did, which was very, very fortunate, we took the guidance parameters out of the guidance system and put them into the guidance system in the lunar module. So the guidance system in the command module knew our attitude with respect to the celestial sphere. So we got that information back into the lunar module’s guidance system — which was dead, we

had to fire it up — and put it in. So we knew then in the lunar module what our attitude was, so we could use the lunar module later on with [its] engine to maneuver to different attitudes. Astronomy: At this stage, you’d already performed a midcourse correction to get off the freereturn trajectory, onto a better path for landing near Fra Mauro. How quickly did Mission Control figure out how to get you back onto that free-return trajectory and to speed the spacecraft up to get you home early? Lovell: It took a little while, but that was the first thing they thought of. It’s kind of interesting. We started out to the Moon on a free-return course, which essentially meant that if our engine quit in the service module, that we were on a course that would take us all the way to the Moon and … with the help of the Moon’s gravity, we’d switch around and come back on a course to the Earth at such an attitude that we could cut into the Earth’s atmosphere.

But then about, I don’t know, 20 hours after we were taking off, going from the Earth to the Moon, they called up and said, “Look, we’ve looked at your situation. When you get around to starting to go down to land on Fra Mauro, we’ve kind of figured out that the Sun is gonna be just above you. So it’s gonna wipe out

The Apollo 13 astronauts would never have made it home safely if they hadn’t figured out a way to remove carbon dioxide from the air. With the help of engineers on the ground, they juryrigged a square canister from the command module to fit into the round holes of the lunar module’s environmental system.

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CLOCKWISE FROM TOP LEFT: Swigert (at right) and Lovell (off camera, to the left) fiddle with some of the temporary hoses and other gear they needed to convert the lunar module into a lifeboat for the trip home. Lovell catches some shut-eye during the long, nerve-wracking journey back to Earth. An oxygen tank explosion on the way to the Moon crippled the Apollo 13 spacecraft. The blast blew away a panel on the service module, seen here after the astronauts jettisoned the module shortly before reentering Earth’s atmosphere.

Fortunately, when you’re in deep trouble, you learn pretty fast.

everything down below. You’re gonna be like landing in a saucer of milk. So we’re gonna get you off that free-return and put you on a course that when you get around and start landing, you’ll start to see the craters and the shadows and things like that.” So that’s fine. Then, of course, when the accident occurred, we were in a position that, had we not gotten off that course, [we would have gone] around the Moon [and come] back to the Earth, [but] we would miss the Earth completely and we’d end up in a long elliptical orbit, going back out to where the Moon was, back to where the Earth was, back to the Moon; I don’t know, for years, I guess. Astronomy: That’s a little scary. One consequence of the freereturn trajectory was that you set a record for the farthest humans have ever been from Earth. Did you realize that at the time or were you too preoccupied with the tasks at hand? Lovell: No, we didn’t. Although when we came around at the apogee, this time we didn’t slow down, of course. We let the apogee take us back. I looked back at

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ASTRONOMY • APRIL 2020

the Moon and I could see that it’s not the one I saw on Apollo 8. It’s a lot smaller. [But] that’s fine with me because I know we’re not gonna slow down, either. So I’ve got the velocity to not get captured by the Moon, to get back home again. Astronomy: That’s good. The lunar module obviously was never designed to operate as a lifeboat and using it was truly unprecedented. How difficult was it to operate and maneuver the lunar module, running the engines and using that to navigate back home? Lovell: Well, normally a lunar module is like any other vehicle. I mean, when you do things, when you do the controls, they’ll go the way they were designed to go and you learned it that way. But when the explosion occurred and we had to use the lunar module, [we still] needed the command module and its heat shield to get back into the atmosphere. [This is] what happened when I first tried to maneuver the vehicle, before we got to the Moon, to get back on that free-return course [after] the ground gave us the particular attitudes to do it. [When] I started to maneuver in the normal way — it didn’t work. The center of gravity, instead of being in the center of the lunar module like it is normally, was way out in left field someplace, and if I wanted to go right, it went someplace else. If I wanted to go left, it [went someplace else]. So I literally had to learn by the [way it handled] how to maneuver, or how to place my controller to get to the proper position. It took a little while for me to do that. But, fortunately, when you’re in deep trouble, you learn pretty fast. Astronomy: That’s always good. I was curious how the communications between you and Mission Control worked out. You were obviously working on the

immediate crisis, while they were planning ahead on how to get you safely home. What was the dynamic like, talking to them and working things out? Lovell: It was pretty good. In the beginning, though … they knew we had to get back on the free-return. … We had a procedure in the computer to slow down and come back again, but we didn’t think the lunar module’s fuel system would handle all that. So they were debating what to do … as we were going towards the Moon. But we talked back and forth. Without Mission Control, I think we wouldn’t be talking today. Astronomy: Is it true that Jack and Fred were captivated with taking photos of the lunar farside? Lovell: [Laughs.] Well, after we got back on the free-return course, the ground came up again and said, “Look it, we have analyzed your situation and the amount of electrical power you have on the lunar module, and it’s fairly touch and go. We think you’ll run out before you get back, and you’re gonna have to have electrical power to get your final position for landing. And so we’re gonna speed you up.” This was on the way to the Moon. So we have a crew down in the simulators now working out the directions. Then, as we got closer and closer to the Moon, they said, “By the way, when you get behind the Moon now, you’ll lose communication with us, so be sure you’re ready to copy [our instructions].” And I said, “Well, I have my two companions, and if I miss something to copy on this next procedure, I’m sure they’ll pick it up.” So as we got very close to the Moon, they call up and say, “Are you ready to copy?” and I said, “I am,” and I started to copy. And I looked at my companions. They weren’t paying any attention.

They had cameras in their hands. Can you imagine, with cameras in their hands? I said, “Gentlemen, what are your plans here?” They said, “As we go around the farside of the Moon, we’re gonna take some pictures.” And I said, “If we don’t get home, you won’t get them developed.” [Laughs.] But I got the procedures, they got their photographs, and so we came home. Astronomy: How ill did Fred get on the trip back home? Was that a major concern for you? Lovell: Yeah. He got an infection, a bladder infection. He got the chills and things like that. I tried to keep him warm. Every once in a while I’d give him a bear hug and try to heat him with my body. But he hung in there, fortunately. The temperature kept dropping slowly. At first, we didn’t notice it. We were turning off all the electronic equipment that provided the heat, to balance the temperature inside the spacecraft. Finally, when all that stuff was down, it got kind of cold in there. But he hung in.

To the relief of nearly everyone on Earth, the Apollo 13 command module splashed down safely in the South Pacific Ocean on April 17.

They figured out a way of taking a canister from the dead command module, which was square, and trying to fit it into a round hole, which we finally did with duct tape.

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They figured out a way of taking a canister from the dead command module, which was square, and trying to fit it into a round hole, which we finally did with duct tape and everything of that nature. And it worked. This was a miraculous thing, because if that didn’t happen, that carbon dioxide was building up and I don’t know what would have happened then.

FROM TOP: The Apollo 13 crew of Haise, Lovell, and Swigert (left to right) finally breathe a sigh of relief as they step on the deck of their recovery ship, the USS Iwo Jima. On board the USS Iwo Jima, Lovell reads a newspaper story that gives a detailed account of Apollo 13’s successful conclusion.

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Astronomy: On a somewhat lighter note: What was the experience like working on the Apollo 13 film and appearing in it, as well as your association with making the film? Astronomy: What were your thoughts as you splashed down in the Pacific and you knew that you had made it home safely? Lovell: Of course, it was one of pure delight. We were coming back in, and we got through that one other big problem that we had, that we were being poisoned by our own exhalations. The environmental system in the lunar module had just one canister to remove carbon dioxide, and it was designed only for two guys for two days, and we were three guys for four days. So we had to figure out a way of getting rid of the carbon dioxide, which Mission Control did.

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Lovell: It was kind of interesting. As a matter of fact, just after we finally landed and we got on the [recovery ship] Iwo Jima and we’re dusting ourselves off and Fred got into sick bay, we went down to see him and we’re sitting around talking. We said, “You know something. This is an unusual flight. I mean, look what happened. … We ought to write a book about it.” So we decided, well, maybe that’s a good idea. I talked to Jack Swigert at that time and Fred Haise, and then nothing happened for a while. Days went by, or years went by, actually. Then a fellow by the name of

Jeff Kluger called up and he was a writer for Discover magazine. He said, “I’ve always wanted to write a story on NASA and the space program, and I thought 13 was the way to go.” I said, “That’s what we’ve been thinking about.” But by that time, Fred had a job with Grumman and so he wasn’t interested, and Jack had died. … And I said, “Well, let’s do it. We’ll split. We’ll go fifty-fifty. I’ll be the guy that gives some of the information.” I liked his writing, and so that’s what we did. That’s what started out to be Lost Moon. … It’s kind of funny how [the movie] got started. … We hadn’t finished the book yet, when our [agent] said, “Look, there’s some interest in the movies for it.” So I got a call from Ron Howard: “Could you come out and talk to me about this particular story?” It turned out that the son of a flight controller also worked for Ron Howard, and his job was to go through all the books and the scripts and everything that people handed him, to see if they’re worthwhile making a movie. He saw this manuscript, which was not completed, and he went to Ron Howard and he said, “Look at this. I think this would be kind of interesting.” So [Jeff] and I went up and talked to him, and that’s how it all got started. Astronomy: From the Apollo 13 film as well as from your getting safely back home, I think in most people’s minds, Apollo 13 is right up there with, or maybe just a little bit below, Apollo 11 in terms of what people remember about the Apollo program. How does it feel to be part of something that didn’t work, but, in the end, ended up becoming even more famous? Lovell: Well, it did become more famous in the beginning, at least in the eyes of NASA. I have to tell you an interesting story. We came back. It’s a failure. … So the

spacecraft, the command module, which was the only thing left of Apollo 13, really, was in a warehouse down in Florida for about six months. Then, they tried to forget about it. They wanted to go on to Apollo 14 and everything like that. Then France called up, Paris called up, [the] museum at Le Bourget, which was where Lindbergh landed. They asked the Smithsonian, “Do you have any space artifacts that we could have in this museum?” Then the lights came on in the Smithsonian and also NASA, “Well, we can get rid of this spacecraft.” So they exiled Apollo 13 to Le Bourget, and it stayed there for 20 years. About 18 years … after that, I had a classmate that went out there and he saw it and he wrote me a letter. He said, “Do you know where your spacecraft is?” I didn’t at that time. No one told me it was in Le Bourget. Then, later on, a year or so later, my wife [Marilyn] and I were in Paris and we went out to this museum, which was at the airfield there, and there we saw it. We walked up to it. It was still on the cradle that they had rolled it in on. It was all by itself, just about, nothing else around it. The hatch was missing. The instrument panel was missing. The seats were missing. The only thing I saw was … a piece of paper that was stuck on the side that said, “Apollo 13,” and gave the names of the three crew members. … And then Ron Howard made the movie. Of course they made the movie that was shown in France, and all those French people said, “Oh, it’s out there in Le Bourget. Let’s go see it.” Meanwhile, NASA was so embarrassed and the Smithsonian, that a museum out of Hutchinson, Kansas, called the Cosmosphere, offered to go get [it] and bring it back and pay for it — and they did. And all those Frenchmen now were mad because they had

kept it for 20 years, and now it came back here. [Laughs.] Astronomy: Do you recall what the first thing you and Marilyn talked about once you returned after Apollo 13? What did that conversation go like? Did [she] encourage you to find a different career path maybe? Lovell: Well, I have to tell you another interesting story along those lines. About a week or two weeks after we got picked up in Hawaii and then we came back, we had a big press conference of course. All the NASA people came in and all the reporters came in, and TV people and stuff like that, and a lot of the families came in to listen to the whole thing. We were in the auditorium down in the Johnson Space Center. So we started talking about that. At the beginning of the conference, a reporter asked, “Jim, are you gonna ask for another flight? Obviously, this was not successful.” Before that, on Apollo 11 [and] 12, management said, “Look, if there’s a problem with this flight, we’ll get you back and we’ll give you the very next one.” So when that question came up from the reporter, I thought to myself, because management was

right behind us, here was the perfect opportunity to put them on the wall and say yes, because they had not talked to us, the 13, just 11 and 12. I was about ready to say something like that when, out in the audience, I saw a hand go up. Then I saw it go down like this. [Jim gives a thumbs down gesture.] It was my wife. [Laughs.] I could tell. I said, “No. I think this is the last flight I’m gonna make.” [Laughs.] Senior Editor Richard Talcott remembers the anxious moments and ultimate elation of Apollo 13’s journey as if it happened yesterday. His latest book is Space Junk (Ziga Media, 2019).

FROM TOP: Jim Lovell reminisces about the Apollo 13 mission with Senior Editor Rich Talcott. ASTRONOMY: DAVID J. EICHER

Commander Jim Lovell chatted with Astronomy magazine in August 2019 about the Apollo 13 mission. ASTRONOMY: DAVID J. EICHER

“If we don’t get home, you won’t get [the pictures] developed.”

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A near-tragedy in space challenged the crew of Apollo 13. They missed walking on the Moon, but in the end, triumphed. BY DAVID J. EICHER AND BRIAN MAY

The Saturn V stack and its mobile launch tower stand atop the huge crawler-transporter that carried the Saturn V rockets from the Vehicle Assembly Building to launch pad 39A. At the time, these tractors were the largest self-powered land vehicles, reaching speeds of only 1 mph (1.6 km/h). ALL IMAGES: NASA/JSC

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The Apollo 13 lunar module, Aquarius, is shown here still inside the Saturn third stage. The component pictures for this stereo view were taken from the command module, Odyssey, as it approached Aquarius for docking and extraction from the rocket’s third stage. At the controls, Jack Swigert led a crew that was still happily on its way to the Moon, unaware of impending trouble.

There’s a special poignancy to these images of Earth, at a “half-illuminated” phase, taken by the Apollo 13 crew on their way to the Moon on April 12, 1970. These were the last pictures they took of their home planet before the explosion which might have made their return to Earth impossible. Small movements between exposures have produced some very interesting depth effects of the image.

BY THE SPRING OF 1970, the Apollo program was rolling along at full speed. The first landing, and subsequent return trip with loftier scientific goals, were successes. Now, NASA had planned a third mission to the Moon’s surface that would again deepen the scientific return from the venture and increase the complexity of the experiments. Launch for what would be termed Apollo 13 was set for April 11, 1970, and would use the same spacecraft configuration employed for the previous two missions. The crew for Apollo 13 consisted of Commander Jim Lovell, Command Module Pilot Jack Swigert, and Lunar Module Pilot Fred Haise. This was not the original plan, however. By tradition, the rotation would have composed the crew as Commander Gordon Cooper, Command Module Pilot Donn Eisele, and Lunar Module Pilot Edgar Mitchell. But both Cooper and Eisele were on rocky terms with NASA management at this point in their careers, for different reasons — Cooper had a relaxed attitude toward training, and Eisele had failed to impress with Apollo 7 and was involved in an extramarital relationship. Because of the WWW. ASTRONOMY.COM

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The Apollo 13 crew captured this breathtaking view of the crater Tsiolkovsky on April 14, 1970, as they swung around the lunar farside. This prominent feature, never visible from Earth, was named after the famous Soviet engineer Konstantin Tsiolkovsky, following its identification in Luna 3 images. It is 113 miles (180 km) across, with a central peak rising 11,050 feet (3,400 m) above the floor.

political issues, Deke Slayton, the Director of Flight Crew Operations, reconfigured the crew to consist of Alan Shepard, Stuart Roosa, and Edgar Mitchell. However, his superiors rejected the plan, believing that Shepard needed more time to recover from ear surgery to be flight ready. The story then becomes even more complicated. Slayton swapped the crews, placing Lovell’s crew into prime position. At that time, it consisted of Lovell, Haise, and Command Module Pilot Ken Mattingly. Mattingly, age 34, was a Chicago-born naval aviator and aeronautical engineer who had joined the astronaut program in 1966. Three days before launch, however, NASA removed Mattingly from the mission because he had been exposed to German measles. Thus, he was replaced by Swigert. After much tumult, the final crew, hours before launch, consisted of Lovell, Swigert, and Haise. Lovell, age 42, was an experienced NASA veteran. His naval flight background had served him well as he entered NASA’s second astronaut group, and then commenced a spaceflight career that included Gemini VII, Gemini XII, and Apollo 8, the first trans-lunar flight. 30

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With a seat on Apollo 13, Lovell would become the first person to make four trips into space, and the first of three people to fly to the Moon twice. Swigert, age 38, was born in Denver and had become an Air Force pilot, aeronautical engineer, and test pilot before joining the fifth group of NASA astronauts. He studied extensively and became an expert on the Apollo command module, and requested that he become a command module pilot on some mission, which Slayton respected. Fred Haise, age 36, was born in Biloxi, Mississippi, and became an Air Force and Marine Corps fighter pilot and test pilot. Like Swigert, Haise was selected as a member of NASA’s fifth group of astronauts.

been cast out of the impact that created nearby Mare Imbrium. This would make for a compelling geological area to study. The countdown began, and the mission launched on time in the early afternoon of April 11, lifting off high into the sky from launchpad 39A. Shortly after launch, the second-stage engine on the inboard side shut down about two minutes early, but this was compensated for by the outboard engines burning for longer periods. The spacecraft did rise to the

All good … at first With Apollo 13 set for a springtime launch, preparations seemed normal and on schedule. The crafts were named Odyssey (command module) and Aquarius (lunar module, or LM). The mission’s objective was to land in the highlands of the region known as Fra Mauro, named for the 50-mile-diameter (80 kilometers) crater that lay within the area. The region contained unusual geology, and ample amounts of ejecta that had

Deke Slayton (standing, at left) explains a proposed procedure for constructing lithium hydroxide canisters to remove excess carbon dioxide from the lunar module cabin during the Apollo 13 emergency. The CO2 was the biggest threat to the astronauts’ well-being. Members of the operations team listen, from left to right: Howard Tindall, Sigurd Sjoberg, Chris Kraft, and Robert Gilruth.

The farside crater Chaplygin was photographed by the Apollo 13 crew, as their craft came around the Moon, heading straight back toward Earth. Chaplygin is a 76.4-mile-wide (123 km) crater with terraced walls, a smooth floor, and a central peak.

planned altitude of 100 nautical miles (185 km) above Earth in a circular parking orbit. Then, some two hours later, the crew fired engines that set the spacecraft off toward the trans-lunar injection. As this was occurring, the onboard crew and members of the flight crew on the ground, led by Flight Director Gene Kranz, analyzed the engine anomaly and found that it was caused by significant so-called pogo oscillations. These vibrations caused the engine to shut down and alarmed the ground crew; they had been observed previously during the Apollo 6 test mission. The lessons from this flight led to modifications to avoid these oscillations on later flights, by adding a helium gas reservoir to dampen vibrations, an automatic cutoff valve, and simplified propellant valves that the engineers believed would lessen the potential problem. After the typical separation and docking of the command module and the LM, the crew had the craft in the proper configuration and cast the spent third stage engine aside into a lunar orbit. They cruised moonward, anticipating a smooth, three-day trip that would carry them to the geologically interesting area of Fra Mauro.

Then, a bang During the cruise phase, some 56 hours after launch, the crew conducted a live TV broadcast from the capsule and then, some six and a half minutes later, began a variety of tasks. Lovell stowed away the TV camera; Haise secured the LM; Swigert was asked to perform a routine task by the ground controllers. In the service module, he switched on the tank stirring fans in holding containers of hydrogen and oxygen. This periodic exercise mixed the gases, which were at very low temperatures, and allowed the gauges to read the tank contents more accurately. But some two minutes after Swigert did so, the astronauts suddenly heard what they described as a “pretty loud bang.” On gauges, they then observed fluctuations in the craft’s electrical power and the computerautomated firing of attitude control thrusters. At first, for a brief two seconds, the spacecraft lost communications and telemetry with the ground, but the computer reset the antenna, restoring communications. Lovell, Swigert, and Haise were perplexed, and momentarily believed the LM had been struck by a meteoroid. Scrambling to understand the situation,

Lovell uttered the line, “Houston, we’ve had a problem,” which Swigert also stated. Lovell believed the problem was related to an electrical bus, with loss of electrical power on one of the electrical circuits. Then, the crew noticed further alarming troubles. The gauge in oxygen tank No. 2 read “zero.” Soon thereafter, two fuel cells failed. Lovell turned around and looked out the spacecraft window, seeing “some kind of a gas” leaking from the capsule out into deep space. And then, troubling transformed into deeply alarming: Over the next two hours, another oxygen tank, No. 1, slowly depleted its supply of the precious gas, its gauge lagging downward to zero as well. The service module suddenly had no lifegiving oxygen gas left. And if that wasn’t bad enough, the situation turned grave. The command/ service module functioned by creating electrical energy from the combination of hydrogen and oxygen into water, but when the first oxygen tank depleted, the only fuel cell still operating also shut down. This now meant that the craft had only a very limited supply of reserve battery power and a small amount of water left. Scrambling, consulting with the ground controllers, the team decided to WWW. ASTRONOMY.COM

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On April 17, 1970, a few hours prior to the splashdown in the South Pacific, Apollo 13 astronauts shot a short sequence of images of the jettisoned service module from the command module, Odyssey. We used two consecutive frames from this series to construct a stereo view, showing the damage from the oxygen tank’s explosion.

shut down and temporarily abandon the command module, saving it for an Earth reentry. They also opted to crank up power inside the LM, move themselves there, and employ that portion of the craft, in their words, as “a lifeboat.” The situation was dire. The energy, electrical power, and oxygen and water were all extremely limited. Turning the LM into a lifeboat made a return trip to Earth possible; without the LM, none of the astronauts would have survived.

Finding a way home Once the grim nature of the situation became apparent, Kranz directed personnel at Mission Control to abort the mission. This could be done in a variety of ways, as mission planners had created scenarios for anticipated in-flight problems. The most obvious alternative was the so-called Direct Abort Trajectory, which would require firing the service module’s engines in order to spin up the spacecraft’s trajectory and change its velocity by more than 6,000 feet (1,830 meters) per second. When the analysis occurred, some 60 hours into the flight, it would be possible to set the craft on a safe return flight toward home. However, it would 32

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be possible at this stage only if the LM were jettisoned, and this was out of the question because it now served as the life-support system for the crew. So Kranz quickly ruled out the most straightforward, anticipated emergency return option. Kranz and the support crew on the ground also considered whether the service module engine’s fuel could be

burned off, which could be followed by jettisoning the service module, and then using the LM engines designed for a lunar descent to power the craft homeward. But flight controllers worried about ridding the spacecraft of the service module, which would supply valuable heat-shield protection during the Earth reentry. Kranz and his colleagues were also worried about the structural

HOW TO VIEW OUR 3D IMAGES There are two ways to view the images printed in 3D. To free view the images with no mechanical assistance, let your eyes relax as you view the photos as though focusing on a point behind them. At first you will see the two images split into four; as your eyes focus at the correct distance, the middle two images will combine to create a single, crisp 3D image. The outer two images will remain on either side of the 3D image and become blurry. Alternatively, you can use a 3D viewer, such as the Lite OWL viewer designed by Brian May and included with the Mission Moon 3-D book, to view images in 3D. Only 5 by 2.5 inches (134 by 64 millimeters) and 0.1 inch (3 mm) thick, the Lite OWL viewer is designed for easily viewing 3D images in books, magazines, modern and vintage stereocards, and even video or other VR content on your smartphone. You can purchase individual Lite OWL viewers separately at www.MyScienceShop.com

Another view of the damaged service module taken prior to splashdown, clearly showing what had happened: An entire panel (top) had been blown off by the oxygen tank explosion, and the interior damage was substantial. In this view, the S-band antenna is visible above the damaged area, and on the right side are the service propulsion system engine and nozzle.

integrity of the service module, and whether its engines would be safe to use in a rescue scenario. So they wished to avoid employing them if at all possible. Moreover, the spacecraft was approaching the point where a “breakeven” in terms of energy would exist between a direct return to Earth and a circumlunar return — flying around the Moon and slingshotting back toward Earth. Because of this, ground controllers decided to wait on the direct return scenario to instead try the circumlunar approach. This would also give them more time to plan how the return would safely get the astronauts back to Earth. With the circumlunar option, more time would be required, but it would be much less risky and would use the Moon’s gravity to propel the spacecraft home. Because the crew were instructed to chart a course that would get them to the region of Fra Mauro, the craft had departed from its initial trajectory prior to the accident. So, in order to initiate a free-return trajectory that would carry them on the proper orbit, they needed to conduct a short burn with the LM descent engine. This burn lasted about 30 seconds.

Troubleshooting in space Inside Aquarius, the supply of oxygen was critically low, and would be only marginally enough to see the crew back to Earth. On the ground, Kranz plodded along with his team, enlisting Ken Mattingly to help controller John Aaron devise a plan so that Odyssey could be restarted, facilitating the landing on Earth. Kranz simply declared, “Failure is not an option.” As Aquarius approached the Moon, the astronauts were increasingly uncomfortable. They looked down upon the lunar surface, coming as close as 158 miles (254 km) at closest approach on April 15. Lovell gazed onto the surface and lamented the fact that he and Haise would not walk on the Moon. The astronauts then focused on the business of returning to Earth. The temperature inside Aquarius was near freezing, making the conditions hard to bear. Moreover, electrical power was running dangerously low, and Haise was feeling increasingly sick. He was experiencing a urinary infection and running a fever, very low in energy and generally feeling terrible. It was a risky and calamitous situation. The lifeboat was becoming a difficult place in which to remain alive.

The psychology of the crew also began to crumble slightly. Swigert suspected that the craft would not be able to return to Earth, and that flight controllers were withholding that fact from the crew. Haise, feverish and ill, felt that Swigert’s nominal experience may have played a role in causing the accident. Before a fullout argument could get rolling, however, Lovell refocused his colleagues on the mission of getting home. (When I interviewed Lovell many years later, he did tell me that the notion that the three of them would become the first “human popsicles in permanent orbit” was weighing heavily on all of their minds.) Following their closest approach to the Moon’s surface, the crew conducted another burn of the LM descent engine. This had the critical effect of speeding up the return time to Earth by about 10 hours, and also shifting the landing spot from the Indian Ocean to the Pacific Ocean. Kranz and the other controllers felt that, despite the deteriorating conditions, the crew would have sufficient oxygen, electricity, and water to return to Earth on this timetable. This allowed them to avoid a riskier maneuver that would have involved jettisoning the service module. After this key burn of the WWW. ASTRONOMY.COM

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LEFT: Following the successful splashdown of Apollo 13, NASA flight directors celebrate in Mission Control. They are, left to right: Gerry Griffin, Gene Kranz, and Glynn Lunney. RIGHT: This image provides a sea level view of the recovery of Apollo 13 in the South Pacific. Fred Haise steps onto the life raft as Jim Lovell leaves the spacecraft in the background. Jack Swigert is already in the raft. The crew were picked up by helicopter and carried to the waiting USS Iwo Jima.

return cruise home. Further, the backups were in storage, out of reach, and the command/service module lithium hydroxide canisters were incompatible with the LM. So ground controllers worked out a plan, communicated it to the crew, and the astronauts jury-rigged an outfit to accomplish the task, using hoses to connect the cubical command module canisters to the LM’s cylindrical sockets. They later referred to this arrangement as “the mailbox.” LM descent engine, which lasted four and a half minutes, only two small course corrections would be made before approaching the home planet. The grave circumstances of Apollo 13 became a worldwide sensation. Television coverage broke in and reported routinely on the mission, in a special report scenario that harkened back to the assassination of President John F. Kennedy and other tragedies. Updates did not look particularly encouraging for some time, leading to a sense of panic and a feeling that a terrible calamity would result. The small supply of electrical power in the craft did not allow live television broadcasts, so news desks passed on the latest statements and updates, as broadcasters employed models of the spacecraft to try to explain to viewers what was happening and how the mission might end. Lovell later wrote that using the LM as a lifeboat for three astronauts really stretched the limits of what it was intended to do: It was supposed to sustain two astronauts for about a day and a half rather than three astronauts for the four-day return to Earth. The command/ service module produced water as a 34

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byproduct from its fuel cells. But such was not the case with the LM, which employed silver-zinc batteries, and so within the LM, vitally important electrical power and water were in short supply. Oxygen was less of a concern because the LM had enough to spare in order to repressurize the spacecraft’s atmosphere after each lunar surface activity. But Kranz and the astronauts all wanted to minimize the inherent risks, of course, so they powered down the LM as much as possible to preserve supplies. This also helped them keep communications and life-support functions as stable as possible until nearing reentry into Earth’s atmosphere. Another looming problem that worsened as the cruise toward Earth continued was carbon dioxide. This, in fact, proved to be a challenging test for both the controllers and the crew alike. Removing carbon dioxide from the LM’s atmosphere would be critical — too much buildup of this gas would prove fatal. Carbon dioxide removal took place via lithium hydroxide canisters, and the LM lacked the number required to remove sufficient carbon dioxide for the

Back home As the craft approached Earth, the crew would have to power up the command module from scratch. This had never before been tried during a flight. Given the craft’s weak power availability, controllers Aaron and Mattingly proposed a procedure, but they were uncertain. The extremely cold temperatures within the spacecraft, which dropped as low as 39 degrees Fahrenheit (4 degrees Celsius), meant that water had condensed on surfaces and alarmed the crew and controllers, who thought of potential electrical shorts. But this did not, in the end, turn out to be a problem. Another risky maneuver loomed. Before approaching Earth’s atmosphere, the crew would have to separate the LM from the command module. Ordinarily, the astronauts would employ the service module’s so-called reaction control system, with its thrusters, to accomplish this. But the craft’s power failure meant this was not operable, and the service module would be gone before the LM anyway. University of Toronto engineers, led by Bernard Etkin and called on by

Grumman, worked on the problem for a day and proposed pressurizing the tunnel connecting the LM and the command module just prior to reentry. This, they proposed, would push the two craft away from each other. They communicated their slide-rule calculations to Mission Control, who sent them on to the astronauts. The procedure worked. With Apollo 13 approaching home, the world watched, bound by hope. The sustained crisis brought people of all nations together as everyone wished for the astronauts’ safe return. News reports became ever more frantic, and despite the constant analysis, all that could now be done was to wait and hope. As the crew moved toward Earth, they first separated the service module, pushed away from it using the LM’s thrusters, and then photographed the damage on the service module as the two crafts inched apart. They were stunned to see an entire panel on the side of the

service module missing. Safely back within the command module, the crew then jettisoned the LM, and, within Odyssey, began reentry into Earth’s atmosphere. The blackout with Apollo 13 lasted six minutes, longer than expected, which heightened the drama on the ground terrifically. But then, in a flash, communications returned, the craft was spotted, and Odyssey made a splashdown, its chutes out, in the Pacific Ocean, southeast of American Samoa. The amphibious assault ship, USS Iwo Jima, picked up the crew, and the world celebrated. In the end, the most dangerous circumstance in space exploration ended with a triumph. The astronauts missed walking on the Moon, but they lived to walk again on Earth. Lessons from this drama would help fuel the momentum of the Apollo missions to come.

Astronomy Editor David J. Eicher is the author of 23 books on science and history. Brian May is an astronomer and founding member and guitarist of the legendary rock band Queen. This story is adapted from Mission Moon 3-D: A New Perspective on the Space Race, by David J. Eicher and Brian May, foreword by Charlie Duke, afterword by Jim Lovell, © 2018 by London Stereoscopic Co. and MIT Press, Boston.

EXPLORE FROM HOME Mission Moon 3-D: A New Perspective on the Space Race, by David J. Eicher and Brian May (with foreword by Charlie Duke and afterword by Jim Lovell), presents the story of the historic lunar landings and the events that led up to them, told through text and three-dimensional images. Mission Moon 3-D contains new and unique stereoscopic images of the Apollo Moon landings to show what it was like to walk on the lunar surface. The triumph of the Apollo 11 Moon landing takes center stage, with detailed stories and visually stunning images from the lunar missions that followed. The book includes 150 stereo photos of the Apollo mission and space race — the largest group ever published — and presents photos never seen before in stereo. The book delivers a comprehensive tale of the space race. New stories appear from the astronauts, including Jim Lovell’s anecdotes about the perilous return of Apollo 13. Mission Moon 3-D also includes a history of the special and musical movements of the 1960s and beyond that transformed the world, from Vietnam and Woodstock to Live Aid. Don’t miss out on this unique treasure.

MISSION MOON 3-D IS AVAILABLE ONLINE AT www.MyScienceShop.com

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SKY THIS MONTH

Visible to the naked eye Visible with binoculars Visible with a telescope

THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY. BY MARTIN RATCLIFFE AND ALISTER LING

APRIL 2020

Venus slips past two star clusters Venus meets the Seven Sisters early this month in a spectacular show that will appeal to visual observers and photographers alike. It’s the main planetary attraction until the predawn hours, when Jupiter, Saturn, and Mars will dominate the morning sky. And in the third week of the month, the April Lyrid meteor shower makes a fine return during the dark of the Moon. As April opens, a dazzling Venus hangs in Taurus the Bull, just 1.7° below the sparkling Pleiades star cluster (M45). Over the course of a few days, the planet closes in on the sisters. Shining at magnitude –4.6, Venus overpowers the star cluster in brilliance, but the Pleiades holds its own as a starstudded region. Give yourself a treat and grab binoculars to stare at the sight for a while. It’s one you’ll never forget. On April 3, Venus lies closest to the Pleiades, nestled just 16' from Alcyone, the brightest star in the cluster. It’s a cosmic engagement ring, sparkling 36

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Venus passed through the Pleiades star cluster April 3, 2012. Exactly eight years later, the brilliant planet puts on a repeat performance. ALAN DYER

with a radiance hard to match with any terrestrial jewels. Venus is the first object to become visible in the western sky after sunset as twilight descends. Sunset occurs near 7:30 p.m. local daylight time, and Venus stands at nearly 45° altitude due west. Watch as nightfall advances and each star

in the Pleiades pops into view. By 8 p.m., many cluster stars will be visible, particularly through binoculars. The Hyades star cluster, along with reddish Aldebaran, soon join the scene with Taurus. Then comes Orion; high above these two constellations, Gemini the Twins stands

Venus slides through the Seven Sisters N TAU RUS

Pleiades 5 E

d 4 3 April 1

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Path of Venus

0.5° Be sure to watch Venus as it skims the dipper-shaped Pleiades (M45) in early April, appearing among the cluster’s stars on the 3rd. The planet reaches greatest brilliancy late in the month. ALL ILLUSTRATIONS: ASTRONOMY: RICK JOHNSON

watch. An eight-day-old gibbous Moon stands 6° below Pollux on April 1. It moves farther along the ecliptic into Cancer the Crab by April 2, and into Leo April 3. Venus continues its climb through Taurus as April progresses. By April 17 it stands 10° due north of Aldebaran. A crescent Moon returns to the scene April 25 and 26, after a full lap of Earth. It’s 3.5° north of Aldebaran on April 25, and Venus stands 10° higher. The following evening, Venus stands 7° to the right of the waxing crescent Moon in eastern Taurus. The elegant pairing is joined by the V-shaped Hyades below it, with Orion to its southeast, hugging the horizon. Through a telescope, Venus undergoes changes that are caused by a combination of its orbit around the Sun inside that of Earth and its diminishing distance from our planet. All month it shows off a delightful crescent, starting April 1 at 46 percent and slimming down to 25 percent April 30. Its apparent diameter swells from 26" to 39"

RISING MOON I Walled-up perfection PLATO IMPRESSES THE NEWCOMER as

OBSERVING HIGHLIGHT MARS and SATURN make for a colorful and contrasting pair in the early April sky. On April 1, ruddy Mars is just 1° southeast of golden Saturn.

over the same period. The planet reaches greatest brilliancy April 27. There are a few asteroids in Taurus at the same time. These include Vesta, which stands 3.7° due north of Gamma (γ) Tauri (the tip of the Hyades’ V) on the 7th. At magnitude 8.4, Vesta is within easy reach of binoculars. On the 12th, it comes within 40' of Epsilon (ε) Tau. Eleventh-magnitude Metis and 12th-magnitude Hygiea each lie within 5° of the Hyades as well. You’ll have to wait until nearly 4 a.m. for another planet to make an appearance in early April. Jupiter rises at 3:20 a.m. on April 1, and by 2 a.m. on April 30. It’s followed soon after by Saturn and Mars, which stand 6° farther east and rise 20 minutes after Jupiter on April 1. The trio of planets makes a fine sight above the southeastern horizon in the two hours before dawn, rising with the Milky Way. On April 1, Saturn and Mars are separated by merely 1°, having passed their closest the night before. Let’s take a closer look at Jupiter first. The giant planet lies in eastern Sagittarius all month and brightens from magnitude –2.1 to –2.3 during the month. On April 6, the much more distant Pluto stands 45' due south of — Continued on page 42

much as it mesmerizes the experienced selenophile. On the evening of April 1, the large oval is a striking sight in the northern half of the Moon. Black shadows painted onto the canvas of its smooth floor retreat into the eastern wall. Over the next few hours, the rising Sun in the lunar sky shortens them even more. The mountains along the rim are not as sawtooth-shaped as their shadows imply. You can test this yourself by stepping outside near sunset and confirming that your own head isn’t as pointy as its shadow! As an early-month bonus, look just south of the equator, where the Straight Wall casts a thin black shadow almost bisecting a larger crater. The central peaks that formed during the birth of Plato lie below the now-solid surface. Some 3.5 billion years ago, redhot molten lava welled up through cracks but could get no farther than the tall walls. Since then, a handful of modestly small impacts have pitted the frozen floor. With a 6-inch scope and a very steady atmosphere, patient observers can pick out the largest craterlets near the center of Plato. Return to Plato over the next couple of evenings. A higher Sun better shows off the way the walls have slumped into the basin. You can replicate this effect at the beach by digging to different depths in moist sand and watching the sides cave in. It’s also neat to compare the texture just

Plato N E

Mare Frigoris

Plato

Vallis Alpes

Mare Imbrium

This 60-mile-wide crater stands between Mare Frigoris and Mare Imbrium in the lunar far north. CONSOLIDATED LUNAR ATLAS/UA/LPL; INSET: NASA/GSFC/ASU

inside and outside the large ring — while you may not be able to resolve the tiniest features, the smooth crater floor is notably different from the dappled area beyond the elevated rim. Have another look on the 30th to see Plato halfway across the terminator, sporting a bright rim with a jet-black interior. Closer to moonset you’ll see light creeping down the western wall as the Sun rises higher in the lunar sky.

METEOR WATCH I No Moon for April’s best display Lyrid meteor shower

CONDITIONS ARE IDEAL for this

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Active dates: April 14–30 Peak: April 22 Moon at peak: New Moon Maximum rate at peak: 18 meteors/hour

April 22, 2 A.M. Looking east With a New Moon occurring the same day as this annual shower’s peak, viewing conditions for the Lyrids couldn’t be better.

year’s Lyrid meteor shower, which is active between April 14 and 30. The Moon is almost New when the peak occurs April 22 in the predawn hours. The radiant begins in Hercules and migrates one degree per day, eventually reaching Lyra; it climbs high after midnight and is almost overhead in the hour before dawn. The expected zenithal hourly rate is 15 to 20 meteors per hour, which can be observed on the morning of peak an hour before twilight begins. Lower rates occur with the radiant lower in the sky. Meteors can appear anywhere in the sky and many are quite faint, so find a dark location and watch an area at about 45° altitude, away from Lyra. The shower has had some brief elevated rates for short periods; while none are expected this year, it’s always worth keeping count. WWW. ASTRONOMY.COM

37

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The Moon passes 4° south of Neptune, 3 A.M. EDT

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Lyrid meteor shower peaks New Moon occurs at 10:26 P.M. EDT

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Uranus is in conjunction with the Sun, 5 A.M. EDT The Moon passes 0.1° north of asteroid Vesta, 7 A.M. EDT Pluto is stationary, 9 A.M. EDT The Moon passes 6° south of Venus, 11 A.M. EDT

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WWW. ASTRONOMY.COM

39

PATHS OF THE PLANETS UMa AND

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THE PLANETS IN THEIR ORBITS

Uranus Solar conjunction is April 26

Arrows show the inner planets’ monthly motions and dots depict the outer planets’ positions at midmonth from high above their orbits.

Neptune

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THE PLANETS IN THE SKY These illustrations show the size, phase, and orientation of each planet and the two brightest dwarf planets at 0h UT for the dates in the data table at bottom. South is at the top to match the view through a telescope. Venus

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PLANETS Date

Venus Earth

Mercury

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Declination (2000.0)

40

ASTRONOMY • APRIL 2020

April 2020

This map unfolds the entire night sky from sunset (at right) until sunrise (at left). Arrows and colored dots show motions and locations of solar system objects during the month.

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SKY THIS MONTH — Continued from page 37 Jupiter gets a black eye S Jupiter Io W Ganymede’s shadow

Ganymede

April 15, 4:30 A.M. EDT

30"

Observers get a great chance to see this gas giant’s moons in action during April. You can watch Ganymede’s shadow traverse Jupiter’s northern cloud tops on the 15th.

Jupiter. At magnitude 14.8, the famous dwarf planet is a difficult challenge — within reach of imagers but beyond visual observers. Jupiter’s appearance through a telescope is stunning. The broad disk spans 37" at the start of the month and grows to 41" by the end. It’s only three months to opposition, and ardent Jupiter watchers will want to record video frames to capture the best views of the planet. Visual observers can easily catch the dark equatorial belts straddling the equator. Subtle dark belts lie to their north and south, along with smaller features such as dark and white spots that are carried along with the strong winds in Jupiter’s atmosphere. The Great Red Spot makes regular appearances as well. Some of the most engaging events in the night sky are the repeated occultations and eclipses of Jupiter’s four giant moons: Io, Europa, Ganymede, and Callisto. Here’s a sampling of those you can catch — there are many more each month. Ganymede, the largest of the four, casts its shadow onto the northern regions of Jupiter on April 15. The event is already underway as Jupiter rises, and ends at 5:52 a.m. EDT. You can catch Europa 42

ASTRONOMY • APRIL 2020

crossing in front of Jupiter on April 19 beginning at 5:17 a.m. EDT, and ending nearly three hours later (after sunrise on the eastern seaboard but still under cover of darkness farther west). The following morning,

3 

April 20, Io’s shadow treks across the jovian cloud tops starting at 4:43 a.m. EDT. The moon follows at 6 a.m., and it can be tracked in darkness across the western half of the U.S. Sometimes two events occur within minutes of each other, adding to the excitement. April 26 finds Ganymede reappearing from behind Jupiter’s southeastern limb soon after 5:20 a.m. EDT, just as Europa’s shadow begins its transit at 5:18 a.m. EDT at the northeastern limb. Ganymede takes over six minutes to fully reappear, by which time Europa’s shadow is easily visible as well. As mentioned earlier, Saturn rises with Mars on

easily visible asteroids traipse through Taurus this month: Vesta, Metis, and Hygiea.

WHEN TO VIEW THE PLANETS EVENING SKY Venus (west) Uranus (west)

MORNING SKY

Mercury (east) Mars (southeast) Jupiter (southeast) Saturn (southeast) Neptune (east)

April 1 at 4 a.m. local daylight time, and nearly two hours earlier April 30. It lies in western Capricornus and shines at magnitude 0.7, brightening by one-tenth of a magnitude by April 30. Saturn stands 2° north of a Last Quarter Moon on April 15. A telescope will easily reveal the bright ring system that dominates the view of the planet. Their widest span at

COMET SEARCH I A comet floats amid spirals COME ENJOY the unhurried Comet PanSTARRS (C/2017 T2) pace of the telescopic Comet PanSTARRS (C/2017 T2). Arcing N toward its close approach to the Sun in the first week of May, its 9th-magnitude glow is visible in a 4-inch scope from dark country May 1 CAM E LOPAR DAL I S 26 skies. Wait until midmonth for the Moon to slide out of the way. If you are considering a 21 Messier marathon, put T2 in the E first half of the night so it is not Path of Comet 16 11 lost in the haze low on the northPanSTARRS ern horizon later on — and throw a 6 in the spiral galaxy IC 342 as well. Both objects are located in the April 1 IC 342 less-visited constellation of Camelopardalis, but if you visual2° ize folding the Little Dipper across Polaris, you will land smack on magnitude 4.6 Gamma (γ) This visitor from the distant Oort Cloud could reach 8th magnitude this month as it traverses the dim backdrop of Camelopardalis. Camelopardalis, the signpost labeled on the chart. T2 is brighter than M109 (in Ursa Major) and likely more compact and, hence, well defined. Nearby IC 342 contrasts starkly because that large nearly face-on spiral has a lower surface brightness. The galaxy’s diffuse light fades as you go to higher power, but T2 will keep giving and likely reveal a nearly stellar core, with a dense shroud of dust enveloping the invisible nucleus beneath.

LOCATING ASTEROIDS I Keep trucking through Taurus

THE THIRD-LARGEST OBJECT in the asteroid belt, 4 Vesta,

A triple delight before dawn Altair AQUIL A

Jupiter AQUARIUS

Mars

Saturn

CAPRIC ORNUS

SAGIT TARIUS

10° April 9, 1 hour before sunrise Looking southeast The three bright morning planets spread out a bit in April, with Saturn perching midway between Jupiter and Mars on the 9th.

midmonth is 37" and the minor axis is 13", while the disk spans 16". This means the northern pole of Saturn covers the far side of the rings. Note the shadow of the planet falling on their far western side. Saturn is accompanied by a variety of moons, the brightest of which is Titan, shining at 8th magnitude. It’s likely the only one you will see in early April, since Saturn is only about 15° high at the onset of twilight. The fainter moons may have to wait until later in the month, when the planet reaches 25° by 5 a.m. local daylight time. Smaller moons like Tethys, Dione, and Rhea shine between 10th and 11th magnitude, and orbit much closer to Saturn than Titan. Mars begins the month of April 1° southeast of Saturn and shines at magnitude 0.8. The striking color contrast between these two planets is evident to most eyes with good night vision. Rust-colored Mars is distinctly different from the soft yellowish glow of Saturn.

Mars is the next planet beyond Earth’s orbit and consequently moves quickly compared with the more sedentary ringed planet. Its higher velocity carries Mars quickly eastward relative to Saturn’s location; during April, the Red Planet crosses most of Capricornus, ending the month 2.7° due west of Deneb Algedi, a 3rd-magnitude star in the constellation’s northeast region. By April 30, Mars brightens to magnitude 0.4 and is beginning to grow in apparent size, albeit slowly. Opposition is not until October, but already Mars spans more than 7" and soon will begin to show off surface detail to smaller scopes. Right now, it’s small in a 14-inch scope. Mercury shines at magnitude 0.0 on April 1 and you can catch it 3° high in the eastern sky 30 minutes before sunrise. On April 3, Mercury is 1.5° south of Neptune, which lies in the far distance and is too faint to see in twilight. Mercury brightens to magnitude –0.2 by April 10, but the

GET DAILY UPDATES ON YOUR NIGHT SKY AT www.Astronomy.com/skythisweek.

passes Aldebaran, the ruddy eye of the celestial Bull, this month. That meeting makes it fairly easy to swing your scope to the right place. At 300 miles across, the potato-shaped minor planet glows at magnitude 8.5; it will require some patience and a 4-inch scope from the suburbs to pick it up. As Vesta approaches the Milky Way, the background stars become more numerous, making following it a bit like tracking a person disappearing into a crowd. Helping us distinguish Vesta are dust lanes that block out the real profusion of stars in this section of the Perseus spiral arm of our galaxy. The surefire way of confirming which dot is Vesta and which is a star is to make a quick sketch one night, then come back on a following one to see which has moved. There really isn’t enough time in one evening to catch its shift against the background before it sets. From April 11–13, Vesta sits a bit more than 30' north of Epsilon (ε) Tauri. That’s the apparent diameter of the Moon. If you see a star right on the indicated path, you’ve got it! While you are in the region, check out the open star cluster NGC 1647. It contains a few dozen stars ranging from 8th to 11th magnitude. Select an eyepiece that shows a bit more than the whole Moon and wait for your eyes to dark adapt to see the fainter ones popping in. The Moon is but a thin crescent when Vesta passes by, so it will not interfere with our observation of the asteroid this month.

Vesta zips past the Hyades N o May 1

Path of Vesta 26

21

16

NGC 1647

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April 1

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This 8th-magnitude asteroid glides north of the V-shaped Hyades star cluster and 1st-magnitude Aldebaran during April.

increasing brilliance is countered by its elevation dropping slightly lower each morning at the same time before sunrise. See how far you can follow this elusive planet before it succumbs to twilight. Uranus and Neptune are both on the far side of the solar system. You may catch a glimpse of Uranus just after sunset in

early April, or sneak a peek of Neptune not long before sunrise late in the month. Martin Ratcliffe provides planetarium development for Sky-Skan, Inc., from his home in Wichita, Kansas. Alister Ling, who lives in Edmonton, Alberta, has watched the skies since 1975. WWW. ASTRONOMY.COM

43

Astronomy’s editor interviews the executive producer of Cosmos and late, great Carl Sagan’s widow. BY DAVID J. EICHER

ON MARCH 9, the venerated

Ann Druyan is the creator, executive producer, writer, and director of Cosmos: Possible Worlds. The new season premieres March 9, 2020, on National Geographic. MIRANDA PENN TURIN/FOX/NATIONAL GEOGRAPHIC

science series Cosmos will return to TV on the National Geographic Channel. The esteemed astronomer Neil deGrasse Tyson will again host the show, which will present the next chapter in television science with Cosmos: Possible Worlds. The show’s driving force, creator and executive producer Ann Druyan, is known for her large body of work and long association with her late husband, the cherished Carl Sagan. In November 2019, Astronomy Editor David J. Eicher interviewed Druyan about the upcoming series, her life, and her projects.

An imagined human settlement on an exoplanet moon is offered as a reminder that we are capable of greatness. ALL PHOTOS, UNLESS OTHERWISE NOTED: NATIONAL GEOGRAPHIC/COSMOS STUDIOS

Astronomy: Would you begin, Ann, by telling us a little bit about the new season of Cosmos? Druyan: I am absolutely bursting with excitement about it, because it’s a way of examining a bunch of questions that have fascinated me my whole life, and it’s also an opportunity to tell some stories of profiles in scientific courage that are completely unknown and really deserve telling in a moment when the question of what’s true is so urgent. This season of Cosmos emphatically deals with that question, as well as some of the more recent developments in science. It feels to me that this is a moment in the history of science when we are awakening to the other forms of consciousness on this planet, the ways of being alive and of understanding the environment on the part of other life forms on this planet. Inevitably, if you’re interested in astrobiology and you’re interested in the question of intelligent life elsewhere, it requires a certain degree of self-consciousness about the life with whom we share this planet. [This season is] called “Possible Worlds.” So, we are exploring exoplanets, and we are imagining the deepest human future possible. Of course, inevitably, it’s also examining the shadow on that future that we all feel — that we should feel.

It seems to me that in every season of Cosmos, the question has always been: Are we ever going to be able to take the revelations of science to heart in the way that we take art to heart, the way that art affects us? Will we ever be able to really feel those things and awaken from our stupor and act? That’s the big question, I think, of our moment in history. Is there anything that can make us value the things we need to live — our air, our climate, our water — more than we value money? That’s the big challenge. Is there anything that can make us think in the timescales of science, not the timescale of the balance sheet? We have to live with our descendants in mind. That’s the challenge. If Cosmos ever succeeds on any level, to me, that’s the critical one. Astronomy: What led you and your associates to revive the series many years after Carl’s original? Druyan: When Carl was alive, he and I dreamed together of doing another series. It was in our long-term and delightful collaboration with Dr. Steven Soter. We thought of doing a series called Nucleus. We thought of doing a series called Ethos. Each of them would have been, in their own way, kind of a season of Cosmos. But that was, tragically, not to be.

So, after Carl’s death, I wanted to do another season of Cosmos. I joined forces with Steve Soter once again, and we invited Neil deGrasse Tyson to join us. Steve and I created an outline for a new season of Cosmos, and for several years, we went from network to network, three in all. I think much to the horror of Steve and Neil and our other colleague, Mitchell Cannold, every network wanted to do Cosmos, but none of them would give me complete creative control, nor would they give me the money necessary to create the kind of cinematic, transporting experience that I felt very strongly Cosmos had to be. So I was driving these guys crazy by saying no, without having another swing on the trapeze to grab ahold of, and just believing that it was better not to do it at all rather than to do something that would be designed by a network and budgeted by a network. So, it didn’t happen for several years, until I met Seth MacFarlane. We had one of those great Hollywood dinners, where he promised me he would send me to the stars, that he would bring me to Peter Rice, who was then the head of the Fox television network and now has gone on to even greater things — and he did. Seth kept every single one of those promises. He was absolutely passionate in his desire to see Cosmos. Not just that WWW. ASTRONOMY.COM

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pilot?” He pointed to the DVD and he said, “No. That’s your pilot. You’re the only person on Earth who knows how to do this, so go do it.” He gave me absolute and complete creative freedom, and it was a tremendous joy to do it. Besides Seth being our champion to Fox, the other thing that he did was he brought me together with Brannon Braga, who had a distinguished career in doing dramatic television — Star Trek and other series — very successfully. Brannon proved to be the absolute perfect collaborator for the second season of Cosmos, and now this third season of Cosmos. So yeah, I have many stories that I want to tell, and I have a vision of what Cosmos, I think, really is.

In a distant future, when our species has ventured to other planetary systems, our descendants will revere the wonders of a world that is only a memory.

Astronomy: In the second season overall, in 2014, the show had wandered considerably far from just astronomy. We heard about mechanics, chemistry, electromagnetism, and other subjects. Was that a big part of the show, not just to teach about scientific topics, but to teach people how to think scientifically?

Host Neil deGrasse Tyson enters the Palace of Life, an imaginary place of ancient towers hidden by the mists of time and enshrouded in myth. Here, he moves into its largest, most ancient realm, to walk among the life at the bottom of the sea.

Cosmos would be a new season, that Cosmos would be produced, but that it would be on Fox, which was such an irony. Of course, when Carl was alive and we were writing together, we didn’t write for the scientific publications. Well, he did plenty, but we wrote for Parade magazine, which was a Sunday supplement that reached 70 million people. We wrote about climate change. We wrote a piece called “The Warming of the World.” This is going back to the ’90s and ’80s. It’s kind of dismal, actually, to think of how long scientists have been warning about the greenhouse effect of the building-up of carbon dioxide and methane in the atmosphere. But anyway, the would-be producers said no, and then Seth brought us to 46

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Peter. He had missed the first run of the original series and was kind enough to say he would watch the DVD. He watched it with his kids, who were horrified that they were gonna be forced to look at what was then something like a 30-year-old science documentary. But the thing that really turned Peter around was that his kids, after some chuckles at the beginning about Carl’s sideburns or whatever, they became obsessed with the show. They would call him at work and say, “Daddy, when are you going to come home? Can we watch another Cosmos?” That immediately persuaded him that it was time to do it. I was thinking he was going to ask for a pilot. He said, “No. I’m ordering 13 from you.” I said, “Don’t you want a

Druyan: Yes, it was. That was the intention. But also, we are a story-driven species. I fell in love with Michael Faraday a long time ago and I really wanted to tell his story because he embodies, for me, just a perfect subject in Cosmos. First of all, his rise from obscurity, from poverty, from a dysfunctional family, from great hardship, and then the story of Humphry Davy, Faraday’s mentor at first, and the All About Eve kind of quality of that relationship. In a book, I had read that Humphry Davy gave Faraday an assignment to do a chemical experiment that he knew would blow up in his face. Well, I thought, “Wow. That’s a great story.” The idea that he had decided to do something to possibly kill his protégé was just so exciting — but, of course, when we did the research we found out there was no truth to the story, or, perhaps, just the tiniest alloy of some kind of reality. It was clear that he did resent Faraday. Anyway, I love Faraday because, first of all, he was so modest. He was, in a way, probably more responsible for the Industrial Revolution in the modern world than any single person. He couldn’t

In the 1970s, Carl Sagan collaborated with fellow astrophysicist Ed Salpeter to design life-forms with plausible evolutionary histories for longterm survival in the roiling clouds of Jupiter. Among them were “floaters,” vast hydrogen blimps pumping helium and heavier gases out of their interior to retain only the lightest gas, hydrogen.

do the math, which I related to. I loved that he had Maxwell to extrapolate his genius into mathematical equations. The fact that he was a Sandemanian — he was a fundamentalist Christian and working in a laboratory with one of the most outspoken atheists of the day, and the two men adored each other — that was amazing. I just was fascinated by him because he seemed, to me, to be a man who wrestled with depression, and yet was probably one of the most productive minds in human history. So that’s how I got into electromagnetism. Of course, if you understand what Faraday did, the way he understood it in non-mathematical terms, then that’s a doorway into the physics content and into Einstein, who of course memorably kept a portrait of Faraday above him as he worked. For me, Faraday was a three-fer, and I wanted the world to love him as deeply as I do. Astronomy: That’s fantastic. Will the current season also have a mixture of astronomy and other allied sciences?

Druyan: Yes. It has a tremendous amount of biology, of neuroscience, and botany. We venture into many different fields. There’s also some quantum physics. We tried to be far-ranging — and one of the best stories that we tell is about how science required a reunification of different scientific fields in order to explore the world of our solar system and beyond. I’m very proud of this thesis because

This was when Carl was coming of age as a scientist. So, again, we get to tell that story as well as that much larger story of science, and how science matured and changed as a result of our first baby steps into the cosmos. Astronomy: Carl was really there at the dawn of the marriage of astronomy and chemistry, of so-called cosmochemistry.

We tried to be far-ranging — and one of the best stories that we tell is about how science required a reunification of different scientific fields in order to explore the world of our solar system and beyond. I haven’t really encountered it anywhere else. Yet, Carl was very much both a product and an actor in that — a participant and an actor in that change at that time, when geologists and chemists and biologists had no interaction whatsoever. There wasn’t a single professional journal on Earth in which a biologist and a geologist and a chemist professionally had a conversation.

Druyan: Exactly. He was the only shared student of both Harold Urey and Gerard Kuiper. Astronomy: Yes. Druyan: The two people who hated each other so much. Astronomy: Right. WWW. ASTRONOMY.COM

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the monorail cars at the ’64 World’s Fair the Tyson Comet.

most brutal, destructive world war in human history, the greatest bloodletting in human history. Yet, here are these people who are so in love with the future. If they had known what the future was really gonna bring them, they probably would have been terrified. Any reasonable person would be, but they had a passion for the future, and that passion captivated Carl and so many others, with the idea of a world — when you look at Democracity, which was the name of the actual city at the New York World’s Fair in 1939, no slums. No slums. None of the inequality and tragedy. What really excited me was — sometimes I like to just go around on YouTube and just search for things. YouTube is such a treasure trove of great musical performances and history and many things. In my searching, I found Einstein’s opening speech. He opened the New York World’s Fair.

Astronomy: I’ll be darned.

Astronomy: I didn’t remember that. Wow.

Druyan: Yeah. So we go with Neil and his family to that — you know, first with Carl is that magnificent art deco, almost sepia kind of New York World’s Fair, and then with Neil is the Kodachrome World’s Fair that I remember so well, because I lived in Queens and I was a teenager at that moment. My brother worked at the fair, so I was there almost every week. I loved it. One of the things we do in the new

Druyan: It’s a great story, which I tell in the book. We didn’t get a chance to really go into it in the show, but in the book, I had the freedom to write about the fact that Einstein was given the assignment to explain cosmic rays at the opening of the New York World’s Fair. This is how audacious and imaginative these people were, the greatest minds on Earth at that time, before or since for a couple of centuries. They said, “OK, we’ve got this World’s Fair. We’re gonna open it. What are we gonna do? I know what we’re gonna do. We are going to pluck 10 cosmic rays from the cosmos, and we are going to capture them on the roof of the Hayden Planetarium” — no kidding — “on the roof of the Hayden Planetarium, and we are going to transmit that energy from Manhattan to Queens. And after Einstein explains what a cosmic ray is, we are going to use the energy from a cosmic ray to illuminate, to perform the greatest path of illumination in human history, as this sphere bursts into light.” So they said to Einstein, “You have to do it in 700 words.” He said, “Impossible. That’s impossible. I’m not gonna do it. It’s too complicated and we don’t even really understand what they are. So no way.” And they begged him, and he relented. What I think is so brilliant is what his

In the Palace of Life, host Neil deGrasse Tyson encounters Saccorhytus coronarius. When it lived about 540 million years ago, it was microscopic. But in this depiction, it looms large. This creature is the earliest common ancestor we’ve yet found, a physical connection we share with almost every animal on Earth.

Druyan: That was another touchstone for me, for the new season: the idea that dreams are maps. Here’s a working-class kid in a little, really tenement apartment in Brooklyn. He took me to see that apartment, and we actually rang the buzzer and the woman let us look at the apartment. It must have been 40 years ago, but I did see it. Here’s a kid who is lying on the living room rug in his parents’ little apartment in Brooklyn, and he’s mapping out the unfolding over the next 100 years of our exploration of the cosmos. The name of the drawing is “The Evolution of Interstellar Flight.” It’s so amazing to me.

You know, it’s my hope that when the pendulum swings so wildly in one direction towards falsehood and fantasy, that it means that it’s going to be swinging back equally in the other direction. That’s the amazing thing about Carl. He knew how lucky he was because he got to live out his earliest, his wildest dreams. As he wrote so beautifully. When he was 5, he was taken to the 1939 New York World’s Fair. That’s where he realized, as he wrote, that there was such a thing as the future, and that the only way to get to it was science. So, we go with Carl and his parents to the 1939 New York World’s Fair. Then we go along with Neil deGrasse Tyson to the 1964 New York World’s Fair. Because his father was an official, they named one of 48

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season is that we go to the 2039 New York World’s Fair, which is a vision of the future we can still have if we learn to use our science and tie technology with wisdom. As I write in the companion book to the new series, this is where the future became a place that you could visit. It was a democratic vision of the future, small D, but also large D, too, I guess. This is the thing I find so amazing. It’s 1939. The country is still mired in the worst global economic depression ever. It was about five minutes away from the

A crowd gathers to watch the great story of the universe, revealed by the generations of scientific searchers, in the night sky above the 2039 New York World’s Fair.

opening remarks were: “If science,” and I’m paraphrasing because I’m doing this from memory, “If science is ever to become fully realized in the same way that art has, its inner meaning will have to penetrate into the mind of the public.” When he said that, I thought, “That’s the dream of Cosmos.” That’s what Carl and I have been doing all our lives. This is the idea of why people should take science to heart. If you really take the methodology of science to heart, the rules of science, then we would not be in the nightmare predicament that our country finds itself in at this moment. It wouldn’t be like that. We would have taught it to our children, so that they would understand that, above all, it matters what’s true. You can’t lie your way to Mars. You can’t lie your way to the outer solar system and beyond. Because in all those iterations and redundancies and every step of every space program, manned or otherwise, the point is everybody has to get it right. You can’t fudge it. You can’t make it up. You have to tell the truth or else something terrible is going to happen and you will never get to where you want to go.

Astronomy: What is your hope for the new season of Cosmos in terms of influencing young people in how they think? We just talked about what a postmodern, ridiculous world we live in with regard to the truth now. How can Cosmos help young people? Druyan: Well, I would love for it to be an awakening. To thaw that frozen sea inside of us that makes us act as if it’s all business as usual and as if we can just keep carrying on the way we are. That would be wonderful: a new respect for scientists and for the value, the message of science, new standards or old standards of evidence reintroduced into our political culture, so that lying becomes unacceptable, no longer a tenable way to get power. These are survival issues. If Cosmos could awaken those feelings — we feature several scientists in this season who literally were willing to die, to be tortured to death, rather than embrace pseudoscience or lie about science. You know, it’s my hope that when the pendulum swings so wildly in one direction towards falsehood and fantasy, that it means that it’s

going to be swinging back equally in the other direction. I’m 70 years old. I’ve never seen any kind of time in American history like this one. I mean, there has been progress from a very racist, homophobic, antifemale society. We still have miles to go. But we made some progress. Yet, we have devolved in the area of respect for reality. Astronomy: It’s very disheartening to many of us who are working very hard to try to continue the respect for truth and for science that you and Carl worked on so hard. Frankly, the truth, scientific truth, it’s more exciting than the fiction. Druyan: Absolutely. We’re not as good at making up stories as reality and nature. They make up the best stories. And ours, you can see through them. Unless they contain a lot of truth of their own, they wear thin very quickly. David J. Eicher is Editor of Astronomy and was encouraged in 1977 by Carl Sagan to pursue a career in astronomy when he commenced publishing Deep Sky Monthly as a teenage astro enthusiast. WWW. ASTRONOMY.COM

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VISIT THE NE AREST

14 habitable exoplanets

Proxima Centauri

Wolf 1061

Distance: 4 light-years Star type: Red dwarf Habitable planets: 1 (b) Discovered: 2016 Mass: 1.27 Earths Orbit: 11.2 days

b

c b

Barnard’s Star

Gliese 832

Distance: 6 light-years Star type: Red dwarf Habitable planets: 1 (b) Discovered: 2018 Mass: 3.23 Earths Orbit: 232.8 days

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Tau Ceti

Distance: 16 light-years Star type: Red dwarf Habitable planets: 1 (c) Discovered: 2014 Mass: 5.4 Earths Orbit: 35.7 days

GJ 3323 e c g

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Proxima Centauri

Distance: 12 light-years Star type: Yellow dwarf Habitable planets: 1 (e) Discovered: 2017 Mass: 3.93 Earths Orbit: 162.9 days

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Tau Ceti

Wolf 1061

Gliese 832

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From a planet circling Proxima Centauri to several around TRAPPIST-1, life-friendly worlds might be closer than you think.

By 1995, astronomers had detected only one planet around a Sun-like star. Today, we have discovered more than 4,000 extrasolar planets. Of those, only about 50 are considered habitable by the most optimistic projections, meaning they could have liquid water and a rocky surface. And only about 20 likely have Earth-like temperatures.

BY JOHN WENZ

So, if we decided to send off a probe to chart other habitable planets — or somehow even visit them ourselves — where would we go? Here are a few of the nearest places, known as of October 2019. John Wenz is digital producer at Knowable Magazine and a former associate editor of Astronomy.

Gliese 625

Distance: 14 light-years Star type: Red dwarf Habitable planets: 1 (c) Discovered: 2015 Mass: 3.41 Earths Orbit: 17.9 days

Distance: 21 light-years Star type: Red dwarf Habitable planets: 1 (b) Discovered: 2017 Mass: 2.82 Earths Orbit: 14.6 days

d b

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Distance: 24 light-years Star type: : Red dwarf Habitable planets: 1 (c) Discovered: 2011 Mass: 3.8 Earths Orbit: 28.1 days

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TRAPPIST-1

Distance: 17 light-years Star type: Red dwarf Habitable planets: 1 (b) Discovered: 2017 Mass: 2.02 Earths Orbit: 5.4 days

Gliese 625

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Explore the Spring is galaxy season, and no constellation proves it better than this one. BY MICHAEL E. BAKICH

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I

t’s difficult to conceive of how large Virgo is. The Maiden is the second-largest constellation, covering 3.1 percent of the sky. It contains 11 Messier objects, tons of worthy targets from the New General Catalogue, and more faint galaxies than you can count. In this brief guide, I want to remove the intimidation of this constellation’s size and provide a list of the best objects to point your scope at. I list them in order of increasing right ascension. That means the westernmost objects come first and, as you observe, the latter ones rise higher in the sky. Please note that I don’t include any elliptical galaxies in this story. They’re still plotted on the map you’ll find on the following two pages, but I describe the best of them in “The sky’s best elliptical galaxies,” which begins on page 58.

M104

Our first object is the Silver Streak Galaxy (NGC 4216). It lies at the western edge of the Coma-Virgo Cluster of galaxies. From a dark site, a 10-inch telescope will reveal several hundred galaxies here, so take your time and be sure of your identification. NGC 4216 appears as a magnitude 10 streak of light nearly five times as long as it is wide (7.8' by 1.6'). The core is bright, but to see its bulge will require a 12-inch or larger scope. Look for 12th-magnitude NGC 4206 12' to the southwest of NGC 4216. It has a similar appearance to its brighter neighbor. The next target is M61, the first of four Messier objects on our list. It glows at magnitude 9.7 and measures 6.0' by 5.9'. This is a face-on spiral galaxy; however, its arms wind tightly around the

SPREAD AND INSET: ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

A crowded field

M61

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NGC 4535

ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

NGC 4216

ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

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core, so it doesn’t look nearly as good as others of this type. That said, a 12-inch telescope will allow you to see the stubby extensions of two arms. Through really big scopes at high magnification, look for a thick bar that runs north-south through this object. Our next object — NGC 4429 — lies in the heart of the Virgo Cluster. It’s an attractive spiral that measures twice as long as it is wide (5.8' by 2.8') and glows at magnitude 10.2. When you observe it, you’ll spot two nearby 9thmagnitude stars. SAO 100102 lies 2' to the north-northeast, and SAO 100103 lies 5' to the south-southeast. The core of this galaxy spans roughly one-third of its length. You’ll also notice that the halo region is more apparent than in similar spirals. An 8-inch telescope is a great instrument for viewing NGC 4429 at a dark site. Crank up the power past 250x to see all of its details. Less than 2° north of NGC 4429 you’ll find NGC 4435 and NGC 4438, a pair of galaxies called the Eyes. The two glow at magnitude 10.2 and 9.7, respectively, and they’re not small, spanning an area 8.5' by 3'. Some millions of years ago, these star cities came within 16,000 lightyears of each other. If you can view them through a 12-inch scope, try to spot the distorted outer regions of NGC 4438. Done with the Eyes? Head 5° south for the Lost Galaxy (NGC 4535), which often gets overlooked by observers. It glows at magnitude 10.0 and measures 7.0' by 6.4'. This barred spiral boasts a core that far outshines the arms. Through a 12-inch or larger scope, you might notice the central region looks

rectangular. Crank up the power beyond 300x, and you’ll spot two faint spiral arms that begin at the ends of a bar. Also, the northern arm contains a 13th-magnitude star some amateurs have thought is a supernova. Unfortunately, it’s just a foreground star in the Milky Way. The “Lost Galaxy” moniker comes from American amateur astronomer Leland S. Copeland, who wrote that it had a “hazy phantom-like appearance in the amateur telescope.” Next up is the unusual spiral NGC 4536. It glows at magnitude 10.6 and measures 6.4' by 2.6', with arms that extend nearly straight out

DEEP-SKY OBJECTS

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16h

NGC 4435 and NGC 4438

NGC 4536

ADAM BLOCK/NOAO/AURA/NSF

from the core. Near the core, they appear thick and bright. One-third of the way from the core to each arm’s end, however, their brightness and thickness decrease

dramatically. A 7th-magnitude star (SAO 119485) sits just 13' east-northeast of this galaxy. For a wonderful example of interacting galaxies, turn your telescope toward the ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

IN VIRGO

NGC 4438 M86 M84 M90 M89 NGC 4216 NGC 4762 M59 M87 ¡ NGC 4429 M60 l NGC 4567 M58 k

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ASTRONOMY: RICK JOHNSON/RICHARD TALCOTT/ROEN KELLY

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about any size telescope will show M58’s slightly oval structure. Through a 16-inch or larger scope, you should be able to pick out the brighter central bar. Around the bar, a faint halo region represents the galaxy’s tightly wound spiral arms.

NGC 5634

South and east The fourth and final Messier object on our list, the Sombrero Galaxy (M104), is anything but a disappointment. This spiral glows at magnitude 8.0 and measures 7.1' by 4.4'. It’s a great object to show off through a mediumsized scope, but do wait until it stands highest in the south.

NGC 4567 and NGC 4568 DAN CROWSON

Siamese Twins (NGC 4567 and NGC 4568). Under a dark sky, even a 6-inch scope will reveal their overall V shape. To see any detail, however, you’ll need a 12-inch or larger instrument. You can tell these two galaxies apart by remembering that NGC 4568 appears slightly brighter (magnitude 10.9 vs. magnitude 11.3) and a bit longer (4.3' vs. 3.1') than its companion. Oh, boy! Our second Messier object is next. Unfortunately, M90 may be one of the least interesting spiral galaxies you’ll ever observe. That’s too bad, because we tend to expect more from Messier objects. It glows reasonably bright for a galaxy, at magnitude 9.5. And it has some size, too, measuring 10.5' by 4.4'. What you’ll see is an object that measures two times as long as it is wide. M90’s spiral arms wind tightly around it, 56

ASTRONOMY • APRIL 2020

KEN CRAWFORD

however, so unless your scope’s mirror measures 2 feet across, be content to just check this bright galaxy off your list and move on. Next on the list, the barred spiral M58 doesn’t rate much higher than M90. It glows at magnitude 9.6 and measures 5.5' by 4.6'. Just

M104 was the first galaxy for which astronomers detected a large redshift. Redshift measures the speed of an object away from us, caused by the universe’s expansion. In 1912, American astronomer Vesto M. Slipher discovered that the Sombrero Galaxy was moving away

from us at a speed of 2.2 million mph (3.6 million km/h). M104’s lens shape and the dark dust lane that splits it are easy to spot. The galaxy’s two sections have unequal brightnesses — the north outshines the south because M104 inclines 6° to our line of sight. The dust lane, therefore, appears to cross south of center. Through a 4-inch telescope, you may detect the dust lane only near the Sombrero’s center. The core is bright and a large halo surrounds it, extending above and below the sections of the spiral arms nearest the nucleus. The next target, Gamma (γ) Virginis, called Porrima, is one of the most famous double stars in the sky. This binary has been the subject of much research, and astronomers have even written poems about it. Nineteenth-century Royal Navy Admiral William Henry Smyth in his Cycle of Celestial Objects devotes eight pages to this double star. Both components shine at magnitude 3.5 and the separation between them is 2.9". Make a note to revisit Gamma Vir every year or two. The pair is widening and by 2030, the separation will increase to 3.9". Next up, NGC 4731, is not a bright galaxy (magnitude 11.5) but it has several features I think you’ll find worth your observing time. It appears as a highly distorted S shape because it doesn’t travel through space alone. You’ll easily spot its brighter companion: Look only 0.8° to the northwest for magnitude 9.2 NGC 4697, an elliptical galaxy I describe on page 61. Gravitational interaction between these two has nearly destroyed NGC 4731’s spiral arms.

Through a 10-inch telescope, observe NGC 4731’s long, relatively bright central bar. If your observing site is dark, crank up the power past 200x and look at the wide, irregular spiral arms that originate from each side of the bar. The western arm appears somewhat brighter. Tiny bright patches within both arms signal hotspots of star formation. Through a 20-inch or larger telescope, use a nebula filter to increase the contrast of those regions and the galaxy’s older stars. If you want to show someone an edge-on galaxy, the next object on our list will do nicely. Barred spiral NGC 4762 glows at magnitude 10.3. More than four times as long as it is wide (9.1' by 2.2'), NGC 4762 appears as a white line through medium-sized telescopes. You won’t see a central bulge through any size scope. All you will notice is that the core appears ever-so-slightly brighter than the arms. Next up is NGC 4856, a magnitude 10.4 spiral that lies near Virgo’s western border with Corvus. Through an 8-inch telescope at 200x,

GAMMA VIRGINIS HAS BEEN THE SUBJECT OF MUCH RESEARCH, AND ASTRONOMERS HAVE EVEN WRITTEN POEMS ABOUT IT. you’ll see a disk with a small, bright central region. The galaxy stretches more than three times as long as it is wide (4.3' by 1.2') in a northeast-tosouthwest orientation. For those of you using 14-inch or larger scopes, crank the power past 350x and look for a magnitude 13.1 foreground star just barely east of the core. At magnitude 13.9, you might be inclined to skip the next target, planetary nebula IC 972, for less difficult fare. That’s fine if you’re viewing through a 4-inch scope, but if you have a 10-inch or larger instrument, have a look at the faint outer layers of this once Sun-like star. Because of its

small size (43"), IC 972 has a reasonable surface brightness. Better known as Abell 37, this object appears uniformly illuminated with a sharp edge. Our final target is globular cluster NGC 5634. If we’re being honest, Virgo is known for its galaxies. The constellation contains some 200 deep-sky objects brighter than 13th magnitude. Only one — magnitude 9.5 NGC 5634 — is a globular cluster. Point a 4-inch telescope at it, and you’ll see lots of faint stars and one bright orange one — magnitude 8.0 SAO 139967, which sits a bit more than 1' east-southeast of the cluster’s center. The star isn’t

part of NGC 5634, it just happens to lie in the same direction from our viewpoint. The cluster’s stars are condensed, meaning you won’t easily resolve them into individual points. But the backand-forth visibility battle you’ll encounter between the star and the cluster makes for a fascinating observation. As you’ve probably inferred, there are a great many more targets in Virgo. The ones on this list, however, should keep your scope pointed in this constellation’s direction for a full night. Take your time, sit comfortably as you observe, and enjoy the view.

M58

M90

ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

Michael E. Bakich is a contributing editor of Astronomy who loves to spend a night viewing objects in a single constellation. PAUL AND DANIEL KOBLAS/ADAM BLOCK/NOAO/AURA/NSF

WWW. ASTRONOMY.COM

57

The Draco Trio

The sky’s

BEST ELLIPTICAL galaxies Discover a world of massive star cities lurking in the skies of fall and spring. BY MICHAEL E. BAKICH

NGC 205

NGC 147 BERNHARD HUBL

OF ALL THE WONDERS OF THE DEEP SKY,

perhaps those most often overlooked by amateur astronomers are elliptical galaxies. And while it’s true you won’t see spiral arms, star-forming regions, or dust lanes, being patient and picking out the details that are there definitely will make you a better observer. To help you with that goal, I’ve selected 22 of these seldom-observed objects visible during fall and spring evenings from northern latitudes. The winter and summer skies contain few ellipticals because of the presence of the Milky Way, which effectively blocks our view of any that lie behind it. I’ve listed them in order of their right ascensions, so those appearing later in the story also rise later at night. Note that the positions of any of these objects in Virgo are plotted on the chart on pages 54-55.

find magnitude 9.2 NGC 185, which is a dwarf spheroidal galaxy. It touts a higher surface brightness than its companion, although it’s a bit larger, measuring 14' by 12'. A 12-inch telescope reveals an oval halo with a bright core that spans twothirds of the galaxy’s diameter. Our next targets are easy to find. Just locate the Andromeda Galaxy, and look 0.6° northwest of its core. Magnitude 8.1 NGC 205 shines as brightly as M31’s other easy-to-see companion, M32.

ADAMBLOCK/NOAO/AURA/NSF

NGC 205, however, is nearly three times larger (19.5' by 12.5'). M32 lies 0.4° due south of the heart of M31. It also glows at magnitude 8.1 and spans 11' by 7.3'. I’ll forgive you if you choose not to spend too much time observing this pair. After all, M31 is hard to beat. Now we come to a deep-sky object that’s a perfect target for a clear Halloween night: Mirach’s Ghost (NGC 404) in Andromeda. Amateur astronomers call it that because it lies only 6.8' from 2nd-magnitude Mirach (Beta [β] Andromedae). As you might imagine, a magnitude 10.3 galaxy next to a star that bright is pretty difficult to see. This S0-type galaxy — one that has the disk shape of a spiral galaxy but no spiral

DIETMAR HAGER

In the fall The first object on our list, NGC 147 in Cassiopeia, is a satellite galaxy of the Andromeda Galaxy (M31), but not one of the two bright ones nearest it. To find NGC 147, move 1.9° west from magnitude 4.5 Omicron (ο) Cassiopeiae. Look carefully for this challenging object. At magnitude 9.5, it seems bright for a galaxy, but that light is spread over an area 15' by 9.4'. NGC 147 is a dwarf elliptical without much apparent structure. When you do see it, you’ll notice an oval halo a bit brighter than the background glow. The galaxy is ever-soslightly brighter toward the center, so that isn’t a foreground star. Not quite 1° east of NGC 147, you’ll

NGC 404 ANTHONY AYIOMAMITIS

WWW. ASTRONOMY.COM

59

M86 GREG MORGAN

M105 and friends BERNHARD HUBL

arms — floats through space roughly 30 million light-years from Earth. Use high magnification to increase the contrast between the galaxy and the bright star. NGC 404 looks round (6.1' across) and bright with an intense center. Now head south from NGC 404 to magnitude 10.5 NGC 584, a fat, lensshaped galaxy in Cetus. You’ll find it 2.2° northeast of magnitude 3.6 Theta (θ) Ceti. Through an 8-inch scope, you’ll see the broad, bright core taking up threequarters of the galaxy’s length. A bright halo lies outside the core, but it quickly fades to the black of space. NGC 584 measures 4.1' by 2'. Next, move on to the Fornax Dwarf, discovered by American astronomer Harlow Shapley in 1938. At a distance of 60

ASTRONOMY • APRIL 2020

438,000 light-years, it is one of the Milky Way’s nearest dwarf companions. Look for it not quite 3° southeast of magnitude 4.4 Beta Fornacis. Although the dwarf’s magnitude of 8.1 indicates a bright object, its size (12' by 10.2') is such that it covers 17 percent of the area of the Full Moon. Its surface brightness, therefore, is low. Through an 8-inch scope, use an eyepiece that yields a 1° field of view, and slowly sweep the area. What you’re looking for is a faint haze just brighter than the background sky. Our next target is a pair of ellipticals in Eridanus: magnitude 9.8 NGC 1407 and magnitude 10.9 NGC 1400, which lies about 12' to the southwest of its partner. A magnification of 100x through an 8-inch telescope will show both objects well. No matter the size of your instrument, you will not see details other than a thin halo around the brighter galaxy. NGC 1407 lies 1.5° southeast of the magnitude 5.2 star 20 Eridani.

region surrounded by a halo with an edge that’s difficult to define. Although M105 appears circular at low magnifications, crank up the power past 250x and you’ll see that it’s a fat oval about 4' across, orienting northeast to southwest. If you’ve located M105, you probably have seen magnitude 9.9 NGC 3384, which sits a mere 7' to its east-northeast. Through any size telescope, you’ll see NGC 3384 as an oval twice as long as it is wide (5.4' by 2.7') oriented northeastsouthwest. The central region is large and bright, and the outer halo appears faint even through large scopes. For our next elliptical, magnitude 9.7 NGC 4125, head north from Leo to Draco. NGC 4125 forms an equilateral triangle (extending northward) with the top stars in the bowl of the Big Dipper, Dubhe and Megrez (Alpha [α] and Delta [δ] Ursae Majoris, respectively). The galaxy lies 8° from each of those bright stars. Through an 8-inch scope, you’ll see a bright, broadly concentrated oval core with a surrounding haze measuring 6.1' by 5.1'. Larger apertures extend the length of the elliptical galaxy, and some observers have even noted a nearly stellar nucleus. It’s easy to confuse M84 and M86 in Virgo. Both lie midway between Denebola (Beta Leonis) and Vindemiatrix (Epsilon [ε] Virginis). M84 lies a bit more to the west, but M86 is bigger and brighter. It glows at magnitude 8.9 (compared to 9.1 for M84) and measures 12' by 9.3' (compared to 5.1' by 4.1'). M84 has few distinguishing characteristics. Its core is large and definitely nonstellar. Look for a fainter halo that surrounds that core. M86 proves that not all elliptical galaxies are circular. In fact, it appears oval even at low magnifications. Modern galaxy classification schemes lean toward M86 as a lenticular

In the spring A new season brings a galaxy that travels in elite company. M105 lies only 0.8° north-northeast of the great spiral M96 in Leo. Beyond that, this magnitude 9.3 doesn’t offer observers much in the way of detail. The galaxy has a bright central

The Fornax Dwarf CHUCK KIMBALL

(lens-shaped) galaxy, rather than a strict elliptical. Cranking up the power will reveal M86’s starlike core. Staying in Virgo, we can find another of Messier’s ellipticals, M49, which glows at magnitude 8.4 and measures 8.1' by 7.1'. Its oval shape is easy to see. The core occupies the central two-thirds of this object, and a fainter outer region envelops it. Because this galaxy is relatively bright, you can crank up the power and reveal this outer halo. Our next target, also located in Virgo, is one of the best known ellipticals in the sky: M87. To astronomers, M87 is a treasure-trove of science. It’s a colossal object with a mass in excess of 3 trillion Suns and a diameter that may reach half a million light-years. M87 also possesses a huge array of globular clusters, perhaps numbering in the tens of thousands. Visually, however, you could do better. Through any telescope up to 20 inches in aperture, M87 appears circular, about 7' across. Its core stands out as bright, and it spans about one-third of the galaxy’s overall size. To see the famous jet emanating from M87’s nucleus, you’ll have to use a 30-inch or larger telescope under a pristine sky. Two more Messier objects in Virgo, M89 and M59, follow. They glow at magnitudes 9.8 and 9.6, respectively. M59 is slightly larger, measuring 4.6' by 3.6', compared with M89’s 3.4' diameter. Through large amateur telescopes, M89’s outer regions form a faint ring that fades rapidly with increasing distance from its center. M59 shows an oval glow and uniform illumination that only begins to diminish close to the galaxy’s edge. Our final Messier object, also in Virgo, is M60. This bright (magnitude 8.8) but under-observed galaxy lies 1.4° north-northeast of magnitude 4.9 Rho (ρ) Virginis. Through medium-size telescopes, M60 easily shows as a double galaxy. Its companion, spiral NGC 4647, glows three magnitudes fainter, but it’s still well within the grasp of a 6-inch scope. M60 appears just slightly out-ofround (7.1' by 6.1'), but is otherwise featureless and lies less than half a degree east of M59. A low-power telescope/eyepiece combination will reveal them both. At magnitude 9.2, NGC 4697 in Virgo ranks as one of the sky’s brightest galaxies. A small telescope will reveal its

M60 ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

hazy nature and oblong shape (7.2' by 4.7'). Step up to an 11-inch scope, and you’ll see much more detail. Regions outside this galaxy’s core show a threefold variance in brightness, getting fainter as you move farther away. The shape of the bright central region may remind you of a spiral galaxy. In fact, astronomers categorize NGC 4697 as a lenticular galaxy — one with characteristics of both an elliptical and a spiral. You’ll find the Ursa Minor Dwarf (UGC 9749) in the southernmost part of the northernmost constellation. It lies 4.7° south-southwest of magnitude 3.0 Pherkad (Gamma [γ] Ursae Minoris). To view this satellite of the Milky Way, use at least an 11-inch telescope, but don’t crank up the power. In fact, you’ll want to use the lowestmagnification, widest-field eyepiece you own. That’s because this galaxy covers one-and-a-half times more area than the Full Moon. It measures 41' by 26'. It has a respectable magnitude, 10.9, but because that light is so spread out, the Ursa Minor Dwarf has a miserably low surface brightness. The best approach for viewing this object is to head to the darkest observing site you can get to. Then, disengage your telescope’s drive and slowly sweep the dwarf’s region of sky. What you’re looking for is an ever-so-slight increase in the background glow of your eyepiece’s field of view. Our final target, the magnitude 12.0 elliptical NGC 5982, teams up with two spirals — magnitude 11.1 NGC 5985 and magnitude 13.2 NGC 5981 — for one

M87 ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

remarkable view. These three objects lie in Draco in an east-west line less than 14' long. You’ll find them 1.8° east-northeast of magnitude 3.3 Iota (ι) Draconis. NGC 5982 is round, small (3' across), and featureless. NGC 5985, meanwhile, sports faint spiral arms, though you’ll need at least a 12-inch telescope to spot any detail. NGC 5981 is another of the universe’s “needle” galaxies: Thanks to its edge-on orientation, it simply looks like a white line. To see this trio, use a magnification around 100x.

Go observe them As this list shows, elliptical galaxies can offer observers of all experience levels a wide variety of objects. Just set up at a dark site, take your time viewing each object, and try a variety of eyepieces. Oh, and have fun! Michael E. Bakich is a contributing editor of Astronomy who has been observing ellipticals since the 1960s. WWW. ASTRONOMY.COM

61

SECRET SK Y

Reflections on a sunset

How many Suns do you see?

FIGURE 1. Two Suns feature in this beautiful but seemingly weird sunset. ALL IMAGES: EDMUND K. PAROWSKI

BY STEPHEN JAMES O’MEARA Stephen is a globetrotting observer who is always looking for the next great celestial event.

62

A sunset by the sea has a magic all its own. As “the golden apple of the Sun” nears the horizon, it shimmers like a beauty whose tresses unfurl like a glittery path from horizon to shore. Science fiction author Ray Bradbury borrowed “the golden apples of the Sun” — the last line of William Butler Yeats’ 1899 poem “The Song of Wandering Aengus” — to use as the title of his 1953 anthology of short stories and as a metaphor for taking a cupful of fire from the Sun. On February 26, 2019, Edmund K. Parowski of Williams, Arizona, photographed a stunning sunset from the volcanic island of Santorini (Figure 1). This view from Fira on the eastern wall of the collapsed caldera overlooks Nea Kameni (Greek for “new volcano,” in reference to the caldera’s still-emerging central island) and the Aegean Sea beyond. The image captures the feel of the sunsets that have inspired poets for ages. But there is more to the image than meets the eye. Particularly, note the two Suns. As Parowski wrote, “I haven’t seen anything quite like this before. It seems as if both Sun images are casting separate reflections on the water.” Parowski’s is indeed a fascinating shot, worthy of the cover of Isaac Asimov’s short story “Nightfall,” where a world is constantly illuminated by multiple suns. But one has only to look carefully at the image to reveal the secret behind the magic of this sunset. At a glance, it looks as if a strong mirage has created a distorted second Sun to appear well below the true Sun. The second Sun lies just below a band of haze whose bottom edge appears to lie about one solar diameter above the dark water horizon, skirting the second Sun’s upper limb. But this is an illusion whose solution lies in the position of the true horizon.

ASTRONOMY • APRIL 2020

Where water meets sky The apparent horizon is not the true horizon. It only marks the position of a change in the intensity of the water’s rippled surface. The bottom edge of the band of haze marks the position of the true horizon. Between it and the top edge of the dark water lies a bright band of calm water, in which we see the reflection of the Sun. This becomes clear in Figure 2, which Parowski captured when the Sun neared the true horizon. There’s yet another illusion. As Parowski noted, in Figure 1, it appears that the two Suns are creating separate glitter paths. But they’re not. What we see is a compound single glitter path. Far out at The sea, the water appears relatively apparent calm, which would allow for a horizon is near, still-water reflection of the true Sun. The glitter path not the true broadens in the region of dark horizon. water, because the water’s surface is more disturbed with steeper wave fronts. Nea Kameni and its shadow then interrupt the glitter path, which continues to broaden as the rippling water closer to the viewer becomes more agitated, causing the light to spread out over a greater area. Parowski’s image is yet another reminder of edifying words by Yeats: “The world is full of magic things, patiently waiting for our senses to grow sharper.”  As always, be sure to send your thoughts and observations of any curious phenomena to sjomeara31@ gmail.com.

FIGURE 2. Left: The true Sun (near top) reflects in calm water (below), with a fatter glitter path in agitated dark water. Right: The true Sun nears the horizon, just prior to setting. Note the bright region of calm water between the dense horizon haze (in which the true Sun lies) and the dark water below, creating a false horizon. BROWSE THE “SECRET SKY” ARCHIVE AT www.Astronomy.com/OMeara

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63

OBSERVING BASICS

Intermediate and advanced guides

satisfying to the owners of 8-inch Schmidt-Cassegrain telescopes that were in vogue at the time. As the 20th century drew to a close, I added George Kepple and Glen Sanner’s two-volume The Night Sky Observer’s Guide (Willmann-Bell Inc., 1998) to my library. Here was the ultimate constellation guide for Handbooks for binocular and telescopic observers. instruments of all sizes, including the 13.1-inch Dobsonian-mounted reflector I then owned. Not only does it list more than 3,000 clusters, nebulae, and galaxies, but it also includes detailed finder charts and descriptions of celestial targets organized by instrument size, from 10x50 binoculars to 24-inch Dobsonians. Unlike Celestial Objects and Burnham’s, The Night Sky limited the amount of supplementary content. Still popular today, it remains a true “meat and potatoes” guide. My fourth constellation guide is a work in progress. Annals of the Deep Sky, co-authored by Jeff Kanipe and Dennis Webb and published by Willmann-Bell Inc., brings backyard astronomy into the 21st century. Volume 1 (Andromeda, Antlia, Apus, and Aquarius) was released in 2015. As of this writing, seven volumes are available, with the most recent taking us through to the constellation Crux. While still serving the novice, The author’s favorite intermediate and A clear April evening is in the offing. What Annals also addresses the needs of the modern-day advanced astronomical celestial sights will my telescope and I amateur whose sophisticated equipment allows for seriguides are seen on display at his home. explore? It’s time to scour my home astronous scientific contributions. Rather than providing With the help of these omy library for constellation guides — handbooks that extensive lists of stellar and deep-sky objects like the handbooks, you can list deep-sky treats broken down by constellation. previous three guides, Annals concentrates on some of take your observing to the next level. the more noteworthy sights in each constellation. Like I own dozens of guides, of course, but let me tell you GLENN CHAPLE about four of my favorites. The first, a reprint of the Rev. Burnham’s, Annals blends in plenty of astronomical T.W. Webb’s Celestial Objects for Common Telescopes, knowledge, both historical and astrophysical. Because Volume 2: The Stars (Dover Publications, 1962), served Annals is an ongoing and evolving project, the exact me well during my early years as a backyard number of volumes and date of final issue astronomer in the 1970s. When Webb pubhave yet to be determined. lished the first edition in 1859, the default Which of these guides do I prefer? I love Which of telescope was a 3-inch refractor and stellar ’em all! That said, I must admit that my these guides longtime friends Celestial Objects and objects like double stars and variables were the intended targets. Therefore, Celestial Burnham’s are pretty outdated. Nevertheless, do I prefer? Objects for Common Telescopes lists only a I love ’em all! their lists of double stars include some not handful of “clusters, nebulae, and groups,” mentioned in either The Night Sky or Annals. as the true nature of galaxies was still So, if I had to limit my number of constellaunknown at the time. This wasn’t a problem tion guides, I’d go with The Night Sky and for me, however, because my telescope back then was Annals. The former, with its extensive lists, and the lata 3-inch f/10 reflector and I was a double star fanatic. ter, with its informative, up-to-date background mateThings changed in the early 1980s when I began setrial, complement each other perfectly. ting my sights on Messier and NGC objects. I needed a Did I leave out any of your favorite astro guides? Let resource with far wider horizons. In 1966, Lowell me know which ones and why they deserve mention. Observatory staff member Robert Burnham Jr. began I’ll feature them in a future column. expanding and updating Celestial Objects for Common Questions, comments, or suggestions? Email me at BY GLENN CHAPLE Telescopes with a self-published series of loose-leaf [email protected]. Next month: We’ll use a small Glenn has been an guides. Twelve years later, Dover released them in the scope to star-hop through the Coma galaxy cluster. avid observer since three-volume Burnham’s Celestial Handbook: An Clear skies! a friend showed Observer’s Guide to the Universe Beyond the Solar him Saturn through System (Dover Publications, 1978). The expanded lists a small backyard BROWSE THE “OBSERVING BASICS” ARCHIVE scope in 1963. AT www.Astronomy.com/Chaple of stellar and deep-space objects were especially

64

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BINOCULAR UNIVERSE

Going to the dogs

circumstantial. Estimates place 17 Canum Venaticorum at 202 light-years from us, while 15 Canum Venaticorum is at 1,144 light-years. Canes Venatici the Hunting Dogs offers rare binocular treats. Turning our attention to the constellation’s Beta (β) star, we come to Chara, the Greek word for “joy.” The area south of Shining only at magnitude 4.3, Chara is spectral type the Big Dipper’s G0, a yellow dwarf main sequence star that is often referred to as a solar analogue. It’s only 100 kelvins handle is occuhotter, 18 percent more luminous, and 4 percent larger pied by the constellation Canes Venatici, supposedly than our Sun. It’s also believed to be about 2.5 billion a pair of hunting dogs. Last years older. In other words, when we look at Chara, we month, I likened the form of are essentially looking at our future Sun from a distance Canis Minor the Little Dog of just over 27 light-years. Cor Caroli and Chara are separated in our sky by 5°, to a hot dog, since it is customarily drawn from just close enough to squeeze into the same 10x binocular two stars. Unfortunately, we field. Place them both in view on either side of the field. can’t do much better here. Just south of an imaginary line connecting them, you’ll As you can see from this see 6th-magnitude 10 Canum Venaticorum, another type G0 star. But to the line’s north, about 3° due east issue’s Star Dome map (pages 38-39), the figure of of Chara, you might also spot a small, faint blur of grayCanes Venatici is also creish light. That’s the 8th-magnitude spiral galaxy M94. ated from just two stars. Nicknamed the Cat’s Eye Galaxy or Croc’s Eye Galaxy The bright galaxy The brighter of the pair, for its appearance in photographs, M94 is seen nearly M63 in Canes Alpha (α) Canum Venaticorum, is known by the face-on from our perspective. As spirals go, it is small, Venatici appears in a bit more than half our Milky Way in diameter. Despite proper name Cor Caroli. Cor Caroli translates as binoculars as an oval smudge with a “Charles’ Heart.” Most authorities agree that the name its modest size, M94 packs a punch. It is also classified slightly brighter was coined in 1660 by Sir Charles Scarborough, physias a starburst galaxy, where internal density waves are center. R. JAY GABANY cian to King Charles II of England. But exactly which compressing interstellar matter into protostars more Charles’ heart was being memorialized is not well vigorously than in typical spirals. established. Some say the intended honoree was King Although it strikes me as a little fainter than M94, M63 Charles I of England, who was beheaded in 1649 during (the Sunflower Galaxy) is also within reach of 35mm to the English Civil War. Others say it refers to 50mm binoculars. To find it, place Cor Caroli in the southwestern edge of your binocular his son, Charles II, who restored the English field and then glance to the opposite side. You monarchy in 1660. The figure Because Cor Caroli shines at only 3rd should see four stars set in a distinctive right of Canes magnitude, it does not stand out well to the triangle. M63 is just 1° north of Venatici is eye alone. Hunt it down with binoculars and 19 Canum Venaticorum, the star at the trianyou’ll be looking at the prototype of a special gle’s right angle. Look for a thin sliver of light created category of spectral type A suns classified as tilted east-west. Like M94, M63 is classified as from just “magnetic stars.” Studies show that it is abunan Sb spiral galaxy. The marked difference in two stars. dant in mercury and silicon, as well as some appearance is owing to its angle of presentation. While M94 is seen virtually face-on, M63 rare elements, like europium. A 6th-magnitude, type F yellow-white is tilted at a much narrower angle. Although companion orbits Cor Caroli, separated by 19". That’s they are no more than a binocular field apart in our sky, likely too close to resolve through most handheld M63 is substantially farther away, some 26.7 million lightyears to M94’s 17.3 million light-years. Under a dark sky, binoculars, but I can just detect both through my tripod-mounted 16x70s. Give it a try and let me know you might notice a faint star at the western tip of M63. Although it’s often mistaken for a supernova within M63, how you make out. Due east of Cor Caroli are 15 and 17 Canum that star is just a photobomber from the Milky Way. Venaticorum. Together, they make an easy double star Thoughts? Comments? Contact me through my BY PHIL to admire through low-power binoculars. Both appear website, philharrington.net. Until next time, remember HARRINGTON almost identical, with the eastern star (15 Canum that two eyes are better than one. Phil is a longtime Venaticorum) shining at magnitude 6.3, while contributor to 17 Canum Venaticorum glows at magnitude 6. Both Astronomy and the BROWSE THE “BINOCULAR UNIVERSE” ARCHIVE AT author of many books. www.Astronomy.com/Harrington glow pure white. In reality, however, their alliance is just

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ASTRONOMY • APRIL 2020

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ASK ASTRO

Galaxy clusters like MACS J1206.2-0847 stay together because the force of gravity among neighboring galaxies overpowers the force of dark energy — and the expansion of the universe — on the scale of the cluster. ESA/HUBBLE & NASA

Astronomy’s experts from around the globe answer your cosmic questions.

Expanding space QI

IF THE UNIVERSE IS EXPANDING, DOES THE SPACE INSIDE AN ATOM EXPAND, TOO? SINCE THE SPACE INSIDE AN ATOM IS MOST OF ITS VOLUME, THAT MEANS THAT MATTER WOULD BE EXPANDING AT THE SAME RATE. Hugh Cedric Beijing, China

AI

We’ve known since the early 20th century that the universe is expanding — after observations by Edwin Hubble and others showed that other galaxies are almost all moving away from us — and the greater their distance, the faster they’re doing so. Astronomers long expected that this cosmic expansion should be slowing down due to the combined gravitational pull of the universe’s seen and unseen matter. However, in the late 1990s, two teams of astronomers — one led by Brian Schmidt and Adam Riess and the other by Saul Perlmutter — discovered evidence, using exploding stars in other galaxies, that cosmic expansion was not, in fact, slowing down, but actually accelerating. The three team leaders later shared the 2011 Nobel Prize in Physics for this accomplishment. The mysterious culprit, originally conceived of by Albert Einstein and which modern

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ASTRONOMY • APRIL 2020

cosmologists call “dark energy,” produces repulsive gravitational effects that cause the average distance between galaxies to increase faster and faster over time. Determining dark energy’s true nature remains one of the greatest mysteries in theoretical physics today. So, does the existence of dark energy in our accelerating universe mean that space is expanding everywhere, even on small scales such as those inside of an atom, where most of the volume is effectively “empty” space? The short answer is no! And we should all count ourselves lucky that we live in such a universe. Thankfully, the local electromagnetic forces that hold the atom’s positively charged nucleus and negatively charged electrons together, as well as the strong nuclear forces confining the nucleus, are significantly stronger than the potentially disruptive forces of dark energy. On larger scales, electromagnetic and gravitational forces prevent planets and moons from expanding as the universe expands. On still larger scales, the force of gravity that binds together systems like stars, solar systems, galaxies, and galaxy clusters is similarly stronger than the local effects of dark energy, which needs vast swaths of space to cause cosmic-scale accelerated expansion. Still, cosmologists can easily imagine “big rip” universes where dark energy was stronger than these local forces, either early on or at late times in cosmic history. In such universes, dark energy could have prevented stars or galaxies from forming or even eventually ripped apart atoms themselves as the expanding universe accelerated itself into oblivion. Needless to say, if this was such a universe, we wouldn’t be here to discuss it! Andrew Friedman Assistant Research Scientist, University of California, San Diego

QI

AI

WHEN WILL THE SUN BECOME A BLACK DWARF? Isaiah Charnow Irvington, New York

Black dwarfs are the very last stage of Sun-like stars. Currently in its main sequence hydrogenburning phase, our Sun has about 4.5 billion years left before it enters the next stage of its life, puffing up to become a red giant. As a red giant, the Sun will eventually

burn not only hydrogen, but also helium. But after about 1 billion to 2 billion years, it will exhaust its supply of nuclear fuel entirely and its core will contract into a white dwarf made of carbon and oxygen, while the outer layers of its atmosphere drift away as a planetary nebula. White dwarfs are roughly the size of Earth, but the Sun as a white dwarf will be about 200,000 times denser than our planet. These objects no longer burn fuel to generate light or heat, but because they start out hot — 10,000 kelvins or more — and have immensely high density, they continue shining with residual heat and cool slowly. It takes a white dwarf roughly 10 trillion years (nearly 730 times the current age of the universe, which is 13.7 billion years) to cool off enough that it no longer gives off visible light and becomes what astronomers term a black dwarf. So, the Sun won’t become a black dwarf for trillions of years — and, in fact, no black dwarfs exist yet, simply because the universe has not been around long enough to allow even the earliest stars to reach this stage. Alison Klesman Senior Associate Editor

A white dwarf such as IK Pegasi B (lower left) is much smaller than the Sun (also shown, for reference), but hundreds of thousands times denser than Earth. When a white dwarf cools enough that it no longer gives off visible light, it becomes a black dwarf. The Sun won’t become a black dwarf for trillions of years, and even the oldest white dwarfs have not had time to cool enough to become black dwarfs yet. RJHALL, CHRKL/WIKIMEDIA COMMONS

QI

IS IT POSSIBLE TO SEE METEORS ON MARS, OR IS THE ATMOSPHERE TOO THIN? Allan Burger Passaic, New Jersey

AI

We use the term “meteor” to refer to the light produced when material from space enters a planet’s atmosphere. Friction between the air and the fast-moving object creates light. If any part of the object survives to impact the ground, it is called a meteorite.

We do know that meteorites exist on the surface of Mars. As of July 2018, at least six meteorites had been confirmed and formally named, all found by robotic rovers. But could they have produced light on the way down? The answer is yes — despite the atmosphere’s low density, meteors should be visible on Mars. In 2008, researchers announced they’d seen, in data taken by the Mars Global Surveyor satellite, signatures of a meteor shower in the martian atmosphere. The shower had taken place in April 2003, as material from Comet 79P/du Toit-Hartley streaked through the air, leaving a fleeting layer of plasma in the atmosphere about 50 to 59 miles (80 to 95 kilometers) above Mars’ surface. The satellite hadn’t seen the meteors themselves, but it did detect signs of the resulting plasma. From the ground, Mars rovers have also looked to the skies in search of meteors. A June 2, 2005, paper in Nature reported that a streak in the martian sky, imaged March 7, 2004, by the Mars Exploration Rover Spirit, was likely a meteor associated with debris from Comet 114P/Wiseman-Skiff. If so, it is the first image of a meteor seen on another world. However, based on its location and motion, researchers could not rule out the possibility that the streak may have been the defunct Viking 2 orbiter, which still orbits the Red Planet. Additionally, the panoramic cameras on Spirit and its sister Mars rover, Opportunity, were periodically pointed upward to observe the martian sky at night, looking for telltale streaks left by meteors. In composite images taken by Spirit on November 18, 2005 — a time when Mars was passing through the debris trail left by Comet 1P/Halley — three streaks that may be meteor trails through the martian atmosphere appear. However, streaks can also be caused by cosmic rays hitting the camera’s detector — so, again, it’s hard to tell for sure whether the images captured meteors. Alison Klesman Senior Associate Editor

On March 7, 2004, NASA’s Mars rover Spirit captured a streak in the martian sky (enhanced in the inset at upper right). It is likely the first image of a meteor seen on another world. NASA/JPL/ CORNELL/TEXAS A&M

SEND US YOUR QUESTIONS Send your astronomy questions via email to askastro@ astronomy.com, or write to Ask Astro, P.O. Box 1612, Waukesha, WI 53187. Be sure to tell us your full name and where you live. Unfortunately, we cannot answer all questions submitted.

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READER GALLERY

Cosmic portraits

1 1. NOT GIZMO OR GADGET ... Sandqvist 149 in Musca is often called the Dark Doodad. It’s about 30 light-years long and lies 700 light-years away. NGC 4372 is the globular cluster to the right of center. Although it looks like the Doodad’s neighbor, it is, in fact, 19,000 light-years away from us. • Nicholas Clarke

2. WHIRLING AWAY The field around the Southern Whirlpool Galaxy (M83) reveals many smaller and more distant star cities. This object in Hydra is one of the most impressive barred spirals in the sky. It lies 15 million lightyears away. • Fernando Menezes

2

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ASTRONOMY • APRIL 2020

3. HALLOWEEN NEBULA The Ghost of Cassiopeia (IC 63) is a reflection nebula near the star Navi (Gamma [γ] Cassiopeiae). The Ghost got its common name because the brilliance of Navi through a telescope often hides it. IC 63 lies some 600 lightyears away. • Oleg Bouevitch

4. SLASH! Hartl-Dengl-Weinberger 2 (Sharpless 2–200) is an old planetary nebula in Cassiopeia. The more common name for this object is the Bear Claw Nebula. For this image, the photographer captured more than 32 hours of exposures. • Douglas J. Struble

3

5. GOOD MOON RISING The gibbous Moon appears behind the Chesterton Windmill in Warwickshire, England, in this image taken September 17, 2019. The windmill, which was built around 1633, is 36 feet (11 meters) high. The Moon’s image is distorted by the amount of Earth’s atmosphere the Moon’s light must pass through near the horizon. • Jamie Cooper

6. DAWN’S EARLY LIGHT

4

5

The bright zodiacal light rose September 28, 2019, above Lockeport, Nova Scotia. Visible with it are the constellation Orion (upper right) and the night sky’s brightest star, Sirius (right of center). • Barry Burgess

SEND YOUR IMAGES TO:

6

Astronomy Reader Gallery, P.O. Box 1612, Waukesha, WI 53187. Please include the date and location of the image and complete photo data: telescope, camera, filters, and exposures. Submit images by email to readergallery@ astronomy.com.

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BREAKTHROUGH

A LOCAL GROUP DOPPELGÄNGER Dark dust lanes mingle with bright star clusters and glowing gas clouds in the large spiral galaxy NGC 3175. Along with its spiral neighbor, NGC 3137 (which lies well outside this Hubble Space Telescope field), the two island universes anchor a group of about 50 galaxies located 50 million light-years from Earth in the southern constellation Antlia. Known as the NGC 3175 group, this collection looks remarkably similar to our Local Group, where the Milky Way and Andromeda galaxies dominate an assembly of some 50 systems, most of which are dwarf or irregular galaxies. By studying such Local Group analogues, astronomers hope to better understand our own galactic neighborhood. ESA/HUBBLE AND NASA, D. ROSARIO ET AL.

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ASTRONOMY • APRIL 2020

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SOUTHERN SKY

BY MARTIN GEORGE

June 2020

Bright planets rule all night Our first taste of planetary viewing in early June comes during evening twilight. That’s when you’ll find Mercury hanging low in the northwest. The innermost planet reaches greatest elongation June 4, when it lies 24° east of the Sun and stands 8° high 45 minutes after sunset. Mercury appears against the backdrop of Gemini the Twins, some 15° to the west (left) of the constellation’s two brightest stars, Castor and Pollux. Mercury remains on display through mid-June, though it becomes harder to see as it dims and sinks closer to the horizon. A telescope reveals the planet’s crescent-shaped disk. At greatest elongation, Mercury spans 8" and appears 38 percent lit. The disk grows larger and the phase wanes as the month progresses. Later in the evening, the two largest planets steal the show. Jupiter and Saturn appear in the east, gaining about 12° of altitude with each passing hour. The two behave like dancing partners, carrying out their retrograde (westward) motions relative to the background stars near the border between Sagittarius and Capricornus. Jupiter lies just west of this border and rises about a halfhour before Saturn. At magnitude –2.7, the giant planet shines brighter than any other star or planet in the evening sky. For those eager to target Jupiter through a telescope, wait until late evening when it

appears higher and its light passes through less of Earth’s image-distorting atmosphere. The gas giant’s disk spans 46" at midmonth and should show a wealth of cloud-top detail. Also keep your eyes out for Jupiter’s four bright moons, which show up through any instrument. Saturn resides in western Capricornus and trails Jupiter by about 5°. Glowing at magnitude 0.3, the ringed world appears some 15 times fainter than its companion. But in terms of its visual impact through a telescope, Saturn is the winner. In mid-June, the planet’s globe measures 18" in diameter while the rings span 41" and tilt 21° to our line of sight. Saturn also boasts several moons, led by 8th-magnitude Titan, within reach of amateur instruments. You’ll have to wait until near midnight local time for the next planet to appear. Mars rises in the east between 11 p.m. and midnight all month. The Red Planet drifts eastward relative to the background stars, moving through Aquarius before entering Pisces in June’s final week. The ruddy world stands out against this dim backdrop, brightening from magnitude 0.0 to –0.5 during June. Mars’ telescopic appearance continues to improve as its distance shrinks. The planet’s disk swells from 9" to 11" across this month and should show some of the dusky surface markings that have intrigued observers for more than a century.

Although Venus has been a prominent evening object since early 2020, it disappeared in the Sun’s glow in late May. It passes between the Sun and Earth on June 3 and then emerges in the predawn sky by midmonth. On the 15th, it rises more than an hour before the Sun and stands out in the east-northeast as twilight brightens. Gleaming at magnitude –4.2, you won’t mistake it for any other object. By month’s end, Venus rises twoand-a-half hours before our star and shines brilliantly at magnitude –4.7. Throughout this period, the planet lies in Taurus the Bull, not far from the Hyades star cluster. Early risers will want to target Venus through a telescope to see its large, crescent-shaped disk evolving rapidly. On the 15th, the planet spans 54" and shows a 4-percent-lit phase. By the 30th, Venus’ diameter has shrunk to 44" while the Sun illuminates 18 percent of its Earth-facing hemisphere. The June 21 solar eclipse is annular along a narrow path in the Northern Hemisphere, but parts of southern Africa, Madagascar, Indonesia, and northern Australia will experience a partial eclipse. From Darwin, Australia, the event begins at 8h03m UT and reaches maximum at 8h35m, when the Moon obscures 11 percent of the Sun’s diameter.

The starry sky If you look high in the south after darkness falls in June, you

can’t miss the distinctive shape of Crux the Cross. Although the Southern Cross appears nearly upright, inquiring minds might want to know precisely when this orientation occurs. First, it depends on what you mean by the word “upright.” The two axes of the Cross intersect at an angle of 82°, not 90°. However, most people would view the Cross as upright when the line joining Acrux (Alpha [α] Crucis) and Gacrux (Gamma [γ] Cru) — the stars that form the bottom and top of the asterism, respectively — appears vertical. It’s a fortunate coincidence that the Cross looks upright when it lies highest in the sky, a position astronomers call “upper culmination.” That’s because Acrux and Gacrux have nearly the same right ascension, differing by only 4.6 minutes. This slight difference means that the two stars have the same azimuth when they are slightly past culmination, at an azimuth of 183°, just 3° west of due south. From Sydney, Australia, at a latitude of 34° south, this happens at a sidereal time of 12h40m, which occurs at 19h56m local time June 1. Surprisingly, the azimuth and sidereal time necessary to see the Cross as upright change slightly with latitude, with the sidereal time increasing the closer you are to the equator. From 20° south latitude, for example, the sidereal time works out to 12h45m.

STAR DOME

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The all-sky map shows how the sky looks at:

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This map portrays the sky as seen near 30° south latitude. Located inside the border are the cardinal directions and their intermediate points. To find stars, hold the map overhead and orient it so one of the labels matches the direction you’re facing. The stars above the map’s horizon now match what’s in the sky.

NGC 104

HOW TO USE THIS MAP

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Lower-temperature stars appear orange

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The coolest stars glow red Fainter stars can’t excite our eyes’ color receptors, so they appear white unless you use optical aid to gather more light

BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT www.Astronomy.com/starchart.

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Note: Moon phases in the calendar vary in size due to the distance from Earth and are shown at 0h Universal Time.

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Mercury is at greatest eastern elongation (24°), 13h UT Full Moon occurs at 19h12m UT; penumbral lunar eclipse

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The Moon passes 2° south of Jupiter, 17h UT

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The Moon passes 3° south of Saturn, 2h UT

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Mars passes 1.7° south of Neptune, 12h UT

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The Moon passes 4° south of Neptune, 23h UT

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The Moon is at perigee (364,366 kilometers from Earth), 3h38m UT Venus is in inferior conjunction, 18h UT

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CALENDAR OF EVENTS

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The Moon passes 3° south of Mars, 0h UT Last Quarter Moon occurs at 6h24m UT

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The Moon is at apogee (404,595 kilometers from Earth), 0h57m UT

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The Moon passes 4° south of Uranus, 2h UT Mercury is stationary, 20h UT

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The Moon passes 0.7° north of Venus, 9h UT

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Winter solstice occurs at 21h44m UT

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Neptune is stationary, 18h UT

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Venus is stationary, 18h UT

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Asteroid Iris is at opposition, 2h UT First Quarter Moon occurs at 8h16m UT

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The Moon is at perigee (368,958 kilometers from Earth), 2h13m UT

ILLUSTRATIONS BY ASTRONOMY: ROEN KELLY

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