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Home , 2020 UA, AB Aurigae, Adam Steltzner, Alpha Leporis, Antimatter comet, Beta Leporis

2020 ARRIVES AT THE RED p. 24

FEBRUARY 2021

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ON THE COVER Comet C/2020 F3 NEOWISE CONTENTS stormed into our skies in July and 24 put on a spectacular — though relatively brief — show. JOSE CHAMBO

FEATURES COLUMNS 16 COVER STORY 34 48 Strange Universe 14 Top 10 space Dome and Studying BOB BERMAN stories of 2020 Paths of the with amateur images Secret Sky 58 An international fleet of RICHARD TALCOTT; Advances in our STEPHEN JAMES O’MEARA set off for Mars, ILLUSTRATIONS BY ROEN KELLY understanding of Crew Dragon carried formation aren’t just Binocular Universe 59 astronauts to the ISS, and 40 coming from large, PHIL HARRINGTON a global pandemic left Corona light professional telescopes. Observing Basics 60 its mark on astronomy. Missed last DAVID MARTÍNEZ-DELGADO GLENN CHAPLE ALISON KLESMAN AND year’s annular AND R. JAY GABANY JAKE PARKS eclipse? We’ve got you 54 7 24 covered with We review Celestron’s QUANTUM GRAVITY New some of the best 60th anniversary C8 Everything you need to begins its mission shots out there. The NexStar Evolution 8HD know about the universe is more than just JAY PASACHOFF With StarSense, a limited this month: OSIRIS- ’s double — it will edition telescope, combines REx overflows, a look at hunt for ancient life, cache 46 all of Celestron’s fanciest the birthplace of , samples, and pave the way for Spend some trappings to produce a superb, a twisted , human explorers. JIM BELL in top-of-the-line instrument. and more. With three Messier objects DAVID J. EICHER 32 and loads of other bright Sky This Month targets, the Charioteer has a 62 IN EVERY ISSUE Twilight planets delight. lot to offer. MICHAEL E. BAKICH Ask Astro From the Editor 5 Galactic traffic jam. MARTIN RATCLIFFE AND Astro Letters 6 ALISTER LING New Products 61 Advertiser Index 61 Reader Gallery 64 Breakthrough 66 ONLINE FAVORITES Astronomy Go to www.Astronomy.com My Trips and Sky This Ask Astro (ISSN 0091-6358, USPS 531-350) Shop Tours Week Archives is published monthly by Kalmbach Media for info on the biggest news and Co., 21027 Crossroads Circle, P. O. Box 1612, Perfect gifts for Travel the world A daily digest Answers to all Waukesha, WI 53187–1612. Periodicals postage observing events, stunning photos, your favorite with the staff of of celestial your cosmic paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to informative videos, and more. science geeks. Astronomy. events. questions. Astronomy, PO Box 8520, Big Sandy, TX 75755. Publication Mail Agreement #40010760.

4 ASTRONOMY • FEBRUARY 2021 FROM THE EDITOR

Editor David J. Eicher Design Director LuAnn Williams Belter EDITORIAL A renewal for Senior Editor Mark Zastrow Production Editor Elisa R. Neckar Senior Associate Editor Alison Klesman Associate Editor Jake Parks Associate Editor Caitlyn Buongiorno stargazing Editorial Assistant Hailey McLaughlin ART As I write this in late 2020, the world Contributing Design Directors Kelly Katlaps, Elizabeth M. Weber Illustrator Roen Kelly has been upended by a pandemic for Production Specialist Jodi Jeranek over eight months now. More sig- CONTRIBUTING EDITORS nificant than any health crisis in a century, the Michael E. Bakich, Bob Berman, Adam Block, Glenn F. Chaple Jr., Martin George, Tony Hallas, coronavirus outbreak has changed all our Phil Harrington, Korey Haynes, Jeff Hester, Alister Ling, lives, in some ways perhaps permanently. Stephen James O’Meara, Martin Ratcliffe, Raymond Shubinski, Richard Talcott Despite all the negative aspects of the pan- EDITORIAL ADVISORY BOARD demic — social distancing away from friends , Marcia Bartusiak, Jim Bell, , and family, economic fallout, and, most Alex Filippenko, Adam Frank, John S. Gallagher lll, Daniel W. E. , William K. Hartmann, Paul Hodge, importantly, the terrible toll of death and sick- Edward Kolb, Stephen P. Maran, Brian May, S. , ness — there has been one apparent benefit James Trefil from these circumstances. We’ve seen quite a Kalmbach Media surge of astronomy hobbyists and their neigh- Chief Executive Officer Dan Hickey bors, friends, and acquaintances discovering Senior Vice President, Finance Christine Metcalf Senior Vice President, Consumer Marketing Nicole McGuire The and or rediscovering the sky. Horsehead nebulae Vice President, Content Stephen C. George This year has been a good one for observational astronomy, no Vice President, Operations Brian J. in the winter Milky Vice President, Human Resources Sarah A. Horner Way are among doubt. We had a beautiful naked-eye comet, C/2020 F3 NEOWISE. Senior Director, Advertising Sales and Events David T. Sherman numerous treasures On the days before and following perihelion, July 3, it shone brighter Advertising Sales Director Scott Redmond rediscovered by Circulation Director Liz Runyon housebound than first and displayed magnificent ion and dust tails. For Director of Digital Strategy Angela Cotey skywatchers. Northern Hemisphere observers, the comet was visible all night in Director of Design & Production Michael Soliday Retention Manager Kathy Steele TONY HALLAS mid-July, bright enough to get non- to take notice. Single Copy Specialist Kim Redmond We’ve also had wonderful planetary oppositions this year. Jupiter ADVERTISING DEPARTMENT Phone (888) 558-1544 and Saturn reached their brightest, opposite the Sun in the sky, in Ad Production [email protected] the second and third weeks of July. Perched in the southeast beside Dina Johnston, [email protected] Sagittarius, the two planets gleamed brilliantly. And novice skygazers RETAIL TRADE ORDERS AND INQUIRIES Selling Astronomy magazine or products in your store: were impressed that a pair of binoculars with 10x magnification could Phone (800) 558-1544 reveal the Galilean of Jupiter astride the big planet’s disk. The Outside U.S. and Canada (262) 796-8776, ext. 818 Fax (262) 798-6592 array of planets continued when Mars reached in mid- Email [email protected] October, displaying some of its amazing features for observers and Website www.Retailers.Kalmbach.com astroimagers. CUSTOMER SALES AND SERVICE Phone (877) 246-4835 The joy that we’ve seen in people observing the sky, some for many Outside U.S. and Canada (903) 636-1125 and some for the first time, has never been stronger. I hope that Customer Service [email protected] when the pandemic is resolved, we’ll not forget our rediscovery of US Ad Sales [email protected] this love affair. There is so much out there for us to see, to capture our Ask Astro [email protected] Books [email protected] minds and our imaginations, and to give us amazing perspective on Letters [email protected] the challenges we face on our little blue planet. Products [email protected] Reader Gallery [email protected] Editorial Phone (262) 796-8776 Yours truly, For reprints, licensing, and permissions: PARS International at www.parsintl.com

Copyright © 2021 Kalmbach Media Co., all rights reserved. This publication may not be reproduced in any form without permission. Printed in the U.S.A. David J. Eicher Allow 6 to 8 weeks for new subscriptions and address changes. Single copy: $6.99 (U.S.). Print + digital subscription rate: U.S.: 1 year $58.95. Canadian: Add Editor $12.00 postage. Canadian price includes GST, payable in U.S. funds. All other Follow the international: Add $22.00 postage, payable in U.S. funds, drawn on a U.S. bank. BN 12271 3209 RT. Not responsible for unsolicited materials. Dave’s Universe blog: www.Astronomy. FOLLOW ASTRONOMY com/davesuniverse .com/AstronomyMagazine Follow Dave Eicher .com/AstronomyMag on Twitter: youtube.com/user/AstronomyMagazine @deicherstar instagram.com/astronomy.magazine

WWW.ASTRONOMY.COM 5 ASTRO LETTERS

We welcome Teaching the teacher just making it up. Could that have been a “sighting” of your comments I taught high school for 42 years. I always men- Haidinger’s Brush? — Tim Geddert, Fresno, CA at Astronomy Letters, P.O. Box 1612, tioned the sense of smell could evoke a strong memory Waukesha, WI 53187; or emotional response, but I never knew why this was or email to letters@ true. Then comes along Associate Editor Jake Parks, Thoughts on “Learning the hard way” astronomy.com. who beautifully taught the teacher with his explana- My compliments to Jeff Hester Please include your tion of how smell works in the sidebar for “What does on his article, “Learning the hard name, city, state, and smell like?” in the September issue. To my more way,” in the September issue. It was country. Letters may than 5,000 former students: I apologize for not explain- a succinct explanation about be edited for space and clarity. ing “the why” of the issue as well as Jake Parks can. the workings of the virus, and it — Jim McLeod, Charlotte, NC placed the blame without using names. As a retired registered nurse, I especially appre- ciated it, but was surprised to see a health article in an Seeing colors astronomy magazine, even though it affects everyone. Thank you, Stephen O’Meara, for introduc- Thanks for that very relevant article. — Alice Mack, ing me to Haidinger’s Brush in the October Fort Myers, FL issue. I had never heard of it but will certainly watch for it. Decades ago, I had a shirt, and I believe it had wide hori- Correction zontal stripes of blue and white. When In the article “What does Titan smell like” in the I picked up that shirt, I would often see September 2020 issue, the caption on page 31 incor- yellow bands running vertically across rectly stated the diameter of Titan is about 1,600 miles A composite image of the pattern. I’d mention it to others, and (2,600 kilometers). Rather, Titan’s radius is about Titan, from the mission. NASA I think they considered me either crazy or 1,600 miles (2,600 km).

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6 ASTRONOMY • FEBRUARY 2021 QUANTUM GRAVITY QG EVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH

SNAPSHOT

TREASURES OF THE G N

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T H G I L F

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L parts of the electromagnetic E B O

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X out powerful blasts Reinhard Genzel and of material that can Andrea Ghez. obstruct our view. WWW.ASTRONOMY.COM 7 QUANTUM GRAVITY OSIRIS-REX OVERFLOWS WITH SAMPLES NASA’s daring mission collected so many rocks that the craft couldn’t contain them all.

TOUCH AND GO. OSIRIS-REx’s sample- collection mechanism makes contact with the surface of Bennu (left) and kicks up a cloud of rocks and dust (right). NASA/ GODDARD/UNIVERSITY OF ARIZONA

OSIRIS-REx is getting ready to Bennu is a dark rubble pile of an The spacecraft’s cylindrical sample- come home — but like a lot of asteroid more than 200 million miles collection head, mounted to a robotic travelers, it has collected more souve- (322 million kilometers) from Earth. arm, pressed into the regolith — the nirs than will fit in its luggage. Launched in 2016, OSIRIS-REx arrived in surface layer of dust and rocks — for This highly relatable problem is a late 2018 and began an intensive survey of six seconds. At the same time, it fired good one to have, though. It means the 1,640-foot-wide (500 meters) world. a canister of gas, kicking up a the spacecraft’s Touch-And-Go (TAG) Right away, Bennu threw the mission cloud of material into a collecting area attempt to collect rocks and dust for a loop. The team expected a smooth inside the rim of the sample head. from the surface of asteroid Bennu surface, like gravel or beach sand. “I must have watched [the video of October 20 was a smashing success. Instead, the landscape was strewn with the TAG attempt] about 100 times last OSIRIS-REx — short for Origins, boulders, forcing a complete overhaul night before I finally got a little bit of Spectral Interpretation, Resource of the craft’s software and a shuteye,” said Dante Lauretta of the Identification, and Security-Regolith painstaking analysis of the asteroid’s University of Arizona, the mission’s Explorer — is now the third mission to surface to identify a safe landing site. principal investigator, at a media nick rocks from an asteroid and NASA’s Nearly two years of work came to frui- briefing on October 21. “I dreamed first, following Japan’s two tion on October 20. First, OSIRIS-REx of a wonderworld of Bennu regolith missions. navigated down to the surface of Bennu. particles floating all around me.”

8 ASTRONOMY • FEBRUARY 2021 QUICK TAKES TWISTED SOLAR SYSTEM READING TEA LEAVES The planets in our solar system Cosmonauts aboard the orbit the Sun on nearly the same International Space Station tracked

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L for more than a decade that this A C

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/ system (right) is surrounded by O S E a disk of gas and dust, and new detected phosphine in the clouds of Venus. The molecule, which is observations show that the stars’ gravitational meddling has formed three associated with biotic processes distinct rings within the disk. The effects have driven the innermost on Earth, may be produced by onto a entirely different plane as the others, shown in this artist’s concept some unknown chemical process (left). The disks aren’t the only crooked objects — the of the stars or even microbial life. (See “Top 10 space stories of 2020” on page 16 themselves are also misaligned in this skewed system. — CAITLYN BUONGIORNO for more information.) ALTERED REALITY Paradox-free time travel is CONTINGENCY PLANS On one hand, that probably means mathematically possible, University Two days after the TAG attempt, OSIRIS-REx collected even more of Queensland researchers find. mission engineers moved the collection material than is visible — perhaps According to their calculations, if head in front of the craft’s to up to 4.4 pounds (2 kilograms), the you traveled back in time and evaluate their haul. Rocks were plainly researchers estimate. “It’s very exciting, interacted with your past self, visible inside the apparatus — at least very surprising, but overall excellent events would adjust themselves 14 ounces (400 grams), they estimated. news,” Lauretta told reporters on around you to ensure a But the team also saw something con- October 23. consistent timeline. cerning: The mylar flap meant to seal in Still, the leaking samples injected a those precious rock samples was stuck sense of urgency into the mission. The DEARTH METAL open. A handful of Bennu particles just team cancelled further evaluations Astronomers have found that stars a few centimeters wide were wedged of their haul to avoid jostling more in the RBC EXT8 in between the flap and the sample head’s particles out of the open flap, instead the have, on inner rim. Furthermore, time-lapse opting to stow it as soon as possible average, 800 times less iron than imagery showed some of the invaluable to minimize losses. By October 28, our Sun, making it the most pebbles escaping into space. It appeared the material had been secured inside metal-poor globular cluster known. the collection head was stuffed full and the craft’s sealed capsule, ready for its MAIDEN FLIGHT literally overflowing. journey back to Earth. The team estimates that the sample China launched an experimental head likely up to a few ounces of reusable spacecraft September 4 material while it was exposed to space. from the Jiuquan Satellite Launch But the remainder still greatly exceeds Center. The craft, which deorbited and landed after a two-day mission the mission’s target of 2.1 ounces (60 g) shrouded in secrecy, is rumored to and is on track to become the largest be a robotic spaceplane akin to the set of asteroid samples ever returned to U.S. Air Force X-37B. Earth by a spacecraft. Scientists hope scrutinizing the MAKING WAVES samples will yield into the In late October, the LIGO and Virgo formation of the solar system, as well observatories announced the RUNNETH OVER. OSIRIS-REx’s sample as life on Earth. They expect to have discovery of 39 gravitational-wave collection head is seen here with Bennu Bennu’s rocks in their labs shortly after particles wafting out. The head’s mylar flap signals caused by binary black (the faint white crescent on the left side of the craft delivers on September 24, 2023. hole or collisions. The the inner rim) is visibly wedged open. NASA — MARK ZASTROW signals, received between April and October 2019, add to 11 previous detections. — M.Z.

WWW.ASTRONOMY.COM 9 QUANTUM GRAVITY

Tangled in a cosmic web But how did these galaxies and the find enough Astronomers have long struggled to material to grow so soon after the Big understand how supermassive black Bang? The key is likely the vast cosmic holes could have formed in the early web. This universal scaffolding is woven universe. Such cosmic goliaths must have through the entire cosmos, connecting formed quickly — less than a billion years distant galaxies, galaxy clusters, and after the Big Bang — defying our cur- galaxy superclusters through threads of rent understanding of how fast a black faint gas known as filaments, which likely hole can feed and grow. Additionally, formed around clumps of dark . it remains unclear exactly where these The authors of the new study giants found huge amounts of matter to think the supermassive black hole A D A

gorge on. Ç and its surrounding galaxies, dubbed L A C

New findings from the European . SDSS J1030+0524, likely fed on gas L / O S

Southern Observatory’s Very Large E that was stockpiled in a tangled knot Telescope, published October 1 in SPIDER’S WEB. This artist’s concept shows six of cosmic web filaments. Astronomy & Astrophysics, may provide recently discovered galaxies surrounding a “The cosmic web filaments are like supermassive black hole in the early universe. It the answer. is the first such tight-knit group of galaxies seen spider’s web threads,” said lead author The paper outlines six newly discov- so soon after the Big Bang. Marco Mignoli in a press release. “The ered galaxies spotted just 900 million galaxies stand and grow where the years after the Big Bang, when the within the cosmos’ first billion years. And filaments cross, and streams of gas — universe was only around 6 percent its at the center of this galactic mosh pit lies available to fuel both the galaxies and current age. This is the first time such a a supermassive black hole a billion times the central supermassive black hole — close grouping of galaxies has been found the mass of the Sun. can flow along the filaments.” — C.B. PLANETARY SURFACE PRESSURES

UNDER PRESSURE. Surface pressure is the pressure exerted on you by VENUS EARTH MARS the weight of the atmosphere above your location. The composition and thickness of a planet’s atmosphere affects the pressure at its surface — a thicker, heavier atmosphere translates to a higher surface pressure. On Earth, the surface pressure at sea level is 1 atmosphere, which is equivalent to 14.696 pounds per square inch (1.033 kg/cm 2). This is how the other terrestrial planets compare to our own, as a ratio of Earth’s surface pressure. — ALISON KLESMAN 092 1 0.01 FAST FACT Y L

This measurement is not possible for L E K

N

the outer planets, whose volumes are mostly E O R

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gas and lack traditional surfaces. They do Y M O N

have solid cores, but these are so deep that O R T S

their location is not exactly known. A

10 ASTRONOMY • FEBRUARY 2021 F S N / I U A / O A R N

, O L L E N G A D

A I H

Source of fast radio bursts revealed P O S

PENT-UP ENERGY. A emits a burst AFTER MORE THAN A DECADE of detective think, could trigger powerful shock of radiation from one side of its in work, astronomers have found the waves with the stunning magnetic this artist’s concept. best evidence yet for the cause of fast properties needed to produce FRBs. radio bursts, or FRBs. The culprit? However, we know of only a handful , according to three papers of magnetars in our Milky Way galaxy, published in November 4. and they all seem too tame to cause FRBs have become one of the most these extreme signals. To know for 1/3000 exciting enigmas in astronomy. For sure whether these stars could generate The carbon astronomers, the mystery began with FRBs, astronomers would have to catch a burst of radio waves that traveled a Milky Way magnetar in the act. footprint 1.6 billion light-years and arrived In late April 2020, a magnetar of the 2020 at Earth on July 24, 2001. Lasting dubbed SGR 1935+2154 began blasting meeting of just five milliseconds, it carried as out X-rays near the center of our gal- the European much energy in radio waves as the axy, some 30,000 light-years away. As Astronomical Sun puts out in an entire month. interest in this object built, astrono- Society — Incredibly, it went unnoticed until mers turned ground- and space-based 2006, when it was discovered in telescopes in its direction. They were held virtually archived data. Since then, radio obser- just in time to watch the activity build due to the vatories have spied dozens of FRB to a crescendo: first X-ray bursts, then coronavirus sources, but the nature of the objects gamma rays — and eventually, the pandemic — producing them has proven elusive. blast of a fast radio burst. It was the as a fraction Modeling has indicated that first FRB ever observed in our home of the carbon magnetars could act as “engines” for galaxy, as well as the first FRB clearly footprint of FRBs. Magnetars, short for “magnetic associated with a single object. stars,” are highly magnetic remnants “This discovery paints a picture the previous of massive dead stars. As a magnetar that some — and perhaps most — of year’s flares, it sends out blasts of energetic these fast radio bursts from other gal- in-person particles. Its powerful magnetic field axies also originate from magnetars,” meeting in then accelerates these particles around Christopher Bochenek, a graduate Lyon, . the star, where models suggest the student at Caltech and co-author particles ram into material from previ- of one of the studies, said in a press ous flares. Such collisions, researchers conference. — ERIC BETZ

WWW.ASTRONOMY.COM 11 QUANTUM GRAVITY

Simulations zoom in BIRTHPLACE on dark matter OF THE REPEATING HALOS. Inside a simulated STARS region of the universe 2 billion light-years Stars are born within enor- across, large blobs of dark matter are mous clouds of gas and dust. the size of galaxy While the clusters. By zooming in — the first inset is is one of the most famous 700,000 light-years — and closest — examples, across, while the second inset is just the is some

600 light-years : G

500 times larger, making it N I

across — researchers S S E

resolved clumps of another favorite for research- C O R P

dark matter roughly N I E T

ers. This new image from the G R

the size of Earth. A A M M I

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their surprise, the D I R V the western wall of the Carina E A V I D

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terious material that Germany — began by The similarity isn’t T I N S have already spotted a num- K R C E A

makes up more than simulating a universe just visual: Analysis V I A N ber of unexpected structures, R U U (

80 percent of all mat- filled with dark matter. showed that the varia- A / R F O S including a long series of T N C /

ter in the universe. This The result was similar tion in density — from E B R

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parallel ridges possibly V strange stuff permeates to those from previous their center to their I A O R N T /

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galaxy, and clumps of cosmic web of filaments large halos also mirrors V evidence of a strong E R V I E S N B U

dark matter, called halos, and clumps called dark each other. O

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to form. Now, supercom- But the team then could aid the search for A T N R O

being ejected from a newly A I H T puter simulations have took their simulations a dark matter. While dark A K N C I formed star. — C.B. R R E T found that these cosmic step further and focused matter does not interact T A N clumps of dark matter in on a small area, run- with normal matter, it I P look surprisingly alike, ning the entire model should give off a burst no matter their size — again for just that region. of gamma-ray light whether they encompass The team repeated the when it collides with its monstrous galaxy clus- process eight times, equivalent ters or are mini-blobs the effectively zooming in and the particles anni- size of Earth. each time to reveal finer hilate each other. This The results of the and finer details. is most likely to happen simulations, published Prior to these simu- at the centers of dark September 2 in Nature, lations, astronomers matter halos, where show some of the most expected the smallest the density is high. The detailed models con- clumps of dark matter to simulations’ results can structed to date of the look different from the now help astronomers structure of dark matter. largest halos, which may understand how much of The authors — a be the building blocks of this radiation they might team of researchers some galaxy clusters. To be able to detect. — M.Z.

12 ASTRONOMY • FEBRUARY 2021

PLANET CAPTURED R E

IN THE LIGHT OF A T N E C

T H G I L F

DYING STAR E C A P S

D R A D

RESEARCHERS HAVE FOUND D

a Jupiter-sized planet orbiting O G / H C

the remains of an exhausted star some 80 light-years E T L A C away. The international team of astronomers spotted - L P J / A the unlikely pair using NASA’s Transiting S A Survey Satellite (TESS) and data from the retired N . its outer layers and loses most of its mass, leaving The dead star, dubbed WD 1856+534, is a behind a smoldering . Distant objects — the stellar ember of a Sun-like star — only 40 percent within a system, such as and , can the diameter of Earth. That makes it seven times smaller be pulled inward by this disruptive death. But these than the Jupiter-sized planet orbiting it, shown here objects are usually ripped apart by the star’s grav- DWARFED. A Jupiter-sized planet in an artist’s concept. The planet, WD 1856 b, speeds ity. This is the first timdew arsfst ritos nhosmt setarrs, W hDa 1v8e5 6f+o5u3n4, d around its host every 34 hours. For comparison, it takes a planet that managed into th sisu arrvtisitv’se c wonictehp t.i tTsh eh polasnte st tar, may have originated 50 times far- Mercury 88 days to complete a single orbit. sweeping in toward theth esrt awr ady uthrainn igts ictusr rfeinnt oarlb sitt, age of life. The finding alsobe efoxrep baenindgs s wthepet pclossesri absi lthitei es of When a star similar to our Sun runs out of fuel, it star threw off its outer layers, balloons outward, forming a that gobbles where life could managbec toom itnagk ae w hhiotel ddw ealrsf.e where in up any planets in its path. Eventually, the star ejects the universe. — C.B.

Sprites and elves frolic in Jupiter’s skies

Lightning is familiar throughout the away from a cloud, leaving it negatively solar system. But it isn’t the only electri- charged. This triggers sprites above the cal outburst that can occur. Stunning, storm. Elves look more like expanding evanescent events called sprites and doughnuts or rings and form when elves are sometimes seen prancing electromagnetic pulses released during a above thunderclouds on Earth. And thunderstorm slam into the ionosphere. NASA’s spacecraft appears to have Over the past four years, Juno’s also captured these flashes on Jupiter Ultraviolet Spectrograph instrument — the first time these events have captured 11 brief, bright flashes of been observed on another planet. ultraviolet (UV) light lasting between Both sprites (which stands 0.1 and 2.5 milliseconds. They are the for Stratospheric/mesospheric first-ever lightninglike flashes recorded Perturbations Resulting from Intense on Jupiter at UV wavelengths, and also Thunderstorm Electrification) and the first TLEs spotted on another world. elves (Emission of Light and Very The flashes originated exactly where Low Frequency perturbations due to sprites and elves are assumed to form on Electromagnetic Pulse Sources) are a Jupiter, above the water cloud layer where type of transient luminous event, or lightning is generated. Scientists aren’t TLE, lasting only milliseconds. sure which TLEs Juno saw — sprites or Sprites typically have round, blobby elves — but now that they know what to centers that sprout tendrils of light look for, the researchers think it will be I

R upward or downward. They occur when easier to spot these phenomena on Jupiter W S / — A.K. H lightning bolts funnel positive charge and in the clouds of other planets, too. C E T L A C - CHANGING COLORS. On Earth, sprites and elves appear red, thanks to the abundance L P J / of nitrogen in our atmosphere. But in Jupiter’s -dominated atmosphere, these A S A

N phenomena likely appear pink or blue, as in this artist’s concept.

WWW.ASTRONOMY.COM 13 STRANGE UNIVERSE The devil’s in the details What should you really look for through the eyepiece?

This 2004 image of Saturn shows clearly the Cassini division — You’ve heard the cliché about details. But it’s Very cool, but not a fine-detail challenge, since the dark gap between the planet’s A and B celestially inaccurate, because details are observing them requires no more than a $5 toy telescope. rings. Spotting details where we usually discover the sublime — or, Sharp-eyed observers have even claimed to see them like this is what keep at least, they’re what lure our attention. So, what is it unaided. So if you did invest more than $5 and want to us returning to the eyepiece. NASA/JPL/SPACE that we crave to see, time and time again? “open ’er up” to see what the 440-horsepower engine SCIENCE INSTITUTE For the sake of newbies who are just starting on this under your telescope’s hood will accomplish, you’ll want epic adventure of exploring the universe, let’s more of a challenge. help whittle down the long process of deciding But first, a reminder that whatever cosmic where to look. Our theme this month is the wonder you’re after, optics alone aren’t enough. exquisite detail that, I guarantee, you’ll keep Details are If someone gave you the keys to the two trying to observe. where we 6.5-meter Telescopes (along with the For example, everyone enjoys watching usually instruction booklet explaining how to detach Jupiter’s four big moons form a straight line discover the all 30 cables from the echelle spectrograph and with military band precision. As giant sublime. instead insert a nice 30mm visual eyepiece), circles back to its starting point you’d still need a night of good seeing, or atmo- once a week, goes around exactly spheric stillness. Fine detail always requires twice — to the second! And in that same good seeing. Where I live, excellent seeing BY BOB BERMAN interval, completes four revolutions, again with conditions arrive as often as magnetic pole reversals. But Bob’s newest book, one-second accuracy. They’re bright, easy to see, and when they do come — heralded when stars are not twin- Earth-Shattering unique. And no other planet with satellites shares kling in the least — we excitedly look for cool details. (Little, Brown and Jupiter’s lack of axial tilt. Jove’s poles angle a negligible On Jupiter, that starts with the Great Red Spot, the Company, 2019), explores the greatest 3° from vertical. And since its satellites orbit its equator, comically understated name for the universe’s largest cataclysms that have they must line up no matter where in their orbit they hurricane. (Official celestial names rarely serve as wor- shaken the universe. happen to be. thy observing suggestions.) Jupiter’s coolest features may

14 ASTRONOMY • FEBRUARY 2021 be the unnamed cloud details: Between its dark belts, on the equator, diagonal white clouds contain breaks where one can peer deeply down and see actual blue sky, no joke. Some of us routinely seek out those amazing unnamed cobalt sky patches. On Saturn, most observers seeking fine detail first try for the Cassini division. This inky gap between its A and B rings highlights the yawning breach separating the rings’ unique, epic beauty and their names, lazily derived from the alphabet. We often give things letters, like the six stars in M42’s stunning Trapezium and lunar craters around larger ones (Copernicus A, B, C, etc.). It’s not a bad idea, except where exceptional beauty cries out, unanswered, to try to stir a poet on the International Astronomical Union’s naming committee. As for that Cassini break, its impossibly narrow, half-arcsecond width somehow materializes whenever the air is steady. In the entire universe, no other thin dark line is more observed, sought after, or treasured. You get the gist of my criteria. So, I’ll skip any further literary f lourishes and simply list 10 examples of details telescopists try for when observing various celestial objects:

1 Mars: The polar caps and dark surface markings 2 Orion Nebula (M42): Those six Trapezium stars 3 NGC 4575: A silhouetted black dust lane running this edgewise galaxy’s entire length 4 M51: The galaxy’s two spiral arms 5 The Moon: Six craterlets forming a French curve inside Clavius

6 Sirius: Its “Pup” companion star ABOVE: NGC 7000, 7 M87: A single jet of near-light-speed also known as the North America material issuing from the galaxy’s core Nebula, floats in the upper left corner of 8 Mercury: The planet’s Moon-like this image. Can you phases, slight orange color, and subtle dark see the faint outline surface blotch of the continent for which it is named? 9 NGC 7000: The outline of North America DENNIS HARPER LEFT: M51 (on the 10 The Horsehead Nebula: Anything right) is a face-on resembling the knight from your chess set spiral galaxy with prominent arms that attentive amateurs But what about you? Is there some marvelous detail can glimpse through the eyepiece. you glimpsed long ago and have sought out ever since? STEPHEN RAHN Some enchanting feature the rest of us should hunt for? Share it! That’s the point of this column. Let’s make it a contest — the winner gets to replace the names of Saturn’s A and B rings with more inspira- tional letters.

BROWSE THE “STRANGE UNIVERSE” ARCHIVE AT www.Astronomy.com/Berman

WWW.ASTRONOMY.COM 15 An international fleet of spacecraft set off for Mars, Crew Dragon carried astronauts to the ISS, and a global pandemic left its mark on astronomy. TOP 10 SPACE STORIES OF 2020

Mars and Venus BY ALISON KLESMAN AND JAKE PARKS are geologically 9 active ON FEBRUARY 24, 2020, 2020 WAS A WILD YEAR. Astronomers kicked it off with researchers released the initial the discovery of a distant galaxy group. Closer to home, they results of NASA’s InSight on saw the Milky Way doing the wave and confirmed geologic Mars. Covering the first 10 months activity on Mars. The star Betelgeuse underwent a strange and of the mission, the findings included striking dimming event, while naked-eye Comet NEOWISE the conclusion that the Red Planet is took our breath away. And a major announcement about seismically active. Venus sparked intense interest; that researchers are still scruti- Of 174 recorded from nizing the result is a signal that science is working as it should. February to September 2019, scien- tists traced two of the strongest to In May, SpaceX’s Crew Dragon capsule ferried astronauts to Fossae. This young region the International Space Station from U.S. soil, the first such has undergone volcanism and other trip in nearly a decade. Two months later, three new missions geologic changes in the last 20 million launched for Mars to usher in a new era of robotic exploration. to 2.5 million years, says Suzanne The global pandemic that defined much of the year changed Smrekar, deputy principal investiga- how scientists worked and shuttered telescopes for months. But tor for InSight. “Mars’ surface is on despite these challenges, our top 10 space stories show how we average several billion years old, so pressed on with new, innovative ways to explore our universe. anything in the million-year range is Earliest galaxy 10 group found THE COSMIC Vithal Tilvi of Arizona State DARK AGES University, who is part of began 380,000 years the Cosmic Deep And after the Big Bang. At first, Wide Narrowband (Cosmic no stars or galaxies existed ) survey seeking to emit light. But even after to understand this era. these objects began forming, Astronomers also aren’t sure their light remained shroud- how fast the transition from ed because the universe was an opaque to a transparent filled with a “fog” of neutral universe occurred. EGS77 (circled in green) is the earliest galaxy group ever discovered. The inset hydrogen atoms that absorb Then the survey found artist’s concept shows how these galaxies are blowing bubbles of ionized hydrogen around them during the era of reionization. NASA, ESA AND V. TILVI (ASU) and scatter ultraviolet light. EGS77: three galaxies shining Over time, energetic ultra- 680 million years after the violet light from early objects Big Bang, when the universe light-years across. These bub- team to spot fainter galaxies ionized these hydrogen atoms, was just 5 percent its current bles overlap, creating a larger, than could be seen if they knocking away their elec- age. “[It’s] the most distant single region of space that’s were alone. trons. This era of reionization group of galaxies — and free of cosmic fog, allowing In the future, Tilvi says, ended 1 billion years after the therefore the earliest group of light to travel freely. “So far we using the same technique will Big Bang, leaving the universe galaxies in the universe — we had [seen] individual galaxies allow researchers to discover transparent to light. have ever seen,” says Tilvi, spread across the survey areas. more faint galaxies. That will But astronomers aren’t whose team published their This is the first time we have ensure astronomers don’t sure exactly what types of find February 27 in The found a group of galaxies” underestimate the number objects — galaxies, black Astrophysical Journal Letters. making the universe transpar- of dim galaxies — which we holes, or stars — were Each galaxy is generating ent, says Tilvi. By virtue of know outnumber bright ones responsible for clearing the a bubble of ionized hydrogen being in a group, EGS77’s — responsible for bringing fog during reionization, says about 2 million to 3 million combined bubbles allowed the about cosmic dawn.

super intriguing,” she adds. “Where’s the features called coronae, which scientists think energy [for the activity] coming from? Why form when faults develop around areas where there and not elsewhere on Mars?” rising magma lifts up the surface. By comparing By late September 2020, InSight had 3D models of how coronae form and evolve recorded about 500 quakes, roughly 50 of with observations of Venus’ surface, the team which give clues about the planet’s deep inte- concluded at least 37 of the planet’s large coro- rior, Smrekar says. By studying how seismic nae are still evolving — indicating the planet is is a young, waves travel through the lower crust, scientists geologically active region of Mars geologically active. have learned Mars’ crust is likely intact — responsible for at least two powerful Smrekar — who is also principal investigator “more like Earth’s than the Moon’s, where the quakes detected by NASA’s InSight of the Venus Emissivity, Radio Science, InSAR, lander. ESA/DLR/FU BERLIN, CC BY-SA 3.0 IGO crust has been pummeled and fragmented by Topography & Spectroscopy (VERITAS) mis- impacts,” she says. “Overall, we are seeing a sion currently under consideration for NASA level of seismicity within the predicted range,” funding, and who worked on the Magellan Smrekar concludes — except when it comes to spacecraft that orbited Venus in the early 1990s bigger quakes, which are rarer than expected. — isn’t surprised. Despite the fact that the idea “It may be that we just need to be patient, or of Venus as a geologically dead planet has per- maybe Mars is behaving in a way that we sisted, she says, “There [have been] a bunch of didn’t anticipate.” recent studies that point to current, geologically But Mars isn’t the only active inner planet. recent activity on Venus.” The large, circular Aine Corona On July 20, a paper in Nature Geoscience dominates this Magellan radar And research into Venus is gaining even added evidence for recent volcanic activity on image of Venus’ surface. New more momentum, as evidenced by No. 2 on this research suggests dozens of these Venus. Researchers led by Anna Gülcher at features are still active on the list. “I’m positive this will lead to great new sci- ETH Zürich in Switzerland looked at circular planet. NASA/JPL ence,” Smrekar says.

WWW.ASTRONOMY.COM 17 Solar science enters 7 a golden age ALTHOUGH THE CLOSEST STAR to Earth has been widely studied, the Sun still maintains some secrets. But perhaps not for long, as a veritable armada of solar science missions may soon unlock the last mysteries. “In my opinion, the most interesting and signifi- cant solar discoveries have been coming from the ,” says Howard, head of the U.S. Naval Research Laboratory’s Solar and Heliospheric Physics branch in Washington, D.C., and principal investigator for Parker’s Wide-field Imager for Solar PRobe (WISPR). Parker, which launched in 2018, “has been making both and remote sensing observations from … much closer to the Sun than ever before.” Recently, the probe revealed that the Sun’s magnetic field is surprisingly complex far from the star. The simple (like a bar magnet) structure researchers expected is there, Betelgeuse blows its nose in our direction 8 IN LATE 2019, Orion the Hunter began having shoulder problems: Betelgeuse, the red that marks the figure’s right shoulder, started dimming dramatically. While astronomers know the star varies regularly over time, this episode was both unexpected and unusually SpaceX’s Crew extreme, noticeable even to naked-eye observers. By Dragon capsule mid-February 2020, the star was just one-third its normal prepares to brightness and the astronomical community was abuzz — dock with the International could this signal an impending supernova explosion? Space Station But, spoiler alert, Betelgeuse remains a fixture in our during the Demo-2 night sky. It’s also back to normal brightness. So, what mission in this happened? An August 13, 2020, paper in The Astrophysical artist’s concept. Journal provides the explanation. Based on Hubble Space SPACEX Telescope observations leading up to the so-called “Great Dimming Event,” the authors concluded the star “sneezed” out a cloud of hot gas from its in fall 2019. By the time it reached millions of miles from the star, the cloud had cooled and condensed into dust grains that temporarily obscured the star’s southern hemisphere and made Betelgeuse appear dimmer. According to study leader Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, events like this can show astronomers how stars like Betelgeuse lose A NEARBY SUPERNOVA? mass — a process that is poorly understood. Despite its continued presence, questions still abound about what we’ll see when Betelgeuse does finally end its life in a brilliant explosion. To observers on Earth, “all this brightness would be In late 2019, Betelgeuse sneezed out a cloud of hot gas. Over concentrated into one point,” says University of California, Santa the next few months, that gas condensed into dust that Barbara, Andy Howell, whose answer is based on blocked a portion of the star’s light, as shown in this artist’s simulations run by two UCSB graduate students, Jared Goldberg and concept. ESO, ESA/HUBBLE, M. KORNMESSER Evan Bauer. “It would be this incredibly intense beacon in the sky that would cast shadows at night, and that you could see during the daytime. Everyone all over the world would be curious about it, because it would be unavoidable.” — Eric Betz, A.K.

18 ASTRONOMY • FEBRUARY 2021 L S S M / L C U

, Sun in mid-June. Its 10 instruments are working as expected B O R

, — or better, says Howard, who is also principal investigator C R W / of the Heliospheric Imager (SoloHI). D O M P

, SoloHI appears less affected by stray light than estimated S P M

, and the observed the signs of a coronal mass S A I

, L

S ejection event. Ultraviolet images show never-before-seen C

; A S bright spots on the Sun. Small and ubiquitous, each is about A N

&

A a millionth to a billionth the size of a traditional solar flare. S E /

M Researchers have christened them “campfires,” and suspect A E T

I

U they are either miniature solar flares or perhaps related to E / R E T

I nanoflares, which are thought to heat the Sun’s outer atmo- B R O

R sphere, the corona. A L O

S The more sensors in the , the better, Howard Solar Orbiter snapped this ultraviolet image of the Sun from halfway between says, because that gives scientists a more comprehensive Earth and our star. It is the closest photo of the Sun ever taken. view. Parker and Solar Orbiter are also joined by the Solar and Heliospheric Observatory, the two Solar Terrestrial Howard says, but overlaid with other structures as well, Relations Observatory probes, the BepiColombo mission, which scientists are now modeling to better understand. and the ground-based Daniel K. Inouye Solar Telescope. Soon to observe in tandem with Parker is the European “I am extremely excited about this ‘golden age’ of solar Space Agency/NASA Solar Orbiter spacecraft. After launch- observations from five different space probes and the ing February 9, 2020, the probe made its first close pass of the ground-based observations,” Howard says.

The launch, which was due to the detection of low streamed online and aired levels of a potentially toxic by all major TV news net- propellant called nitrogen works, was viewed live by tetroxide. After it was some 10 million people. The purged from the spacecraft, following day, the spacecraft the astronauts safely exited docked with the ISS and its the sealed crew cabin, passengers, astronauts proving the privately built and capsule’s worth. Robert Behnken, migrated to On November 15, the the orbiting research first official Crew lab, where they Dragon mission, spent the next dubbed Crew-1, two months blasted off for testing Crew the ISS. After Dragon and docking with carrying out the space sta- science tion the next experiments. day, NASA Once their stint NASA/JSC astronauts Michael on the ISS concluded, the Hopkins, Victor Glover, pair hopped back into Crew and Shannon Walker, as Dragon and set course for well as JAXA home. Shortly after 1:48 P.M. , boarded Crew Dragon ferries CDT on August 2, Hurley the ISS, where, as of the astronauts, a first and Behnken splashed down time of this writing, they 6 in the Gulf of Mexico. The continue to work. SINCE THE (ISS). But that’s not the case capsule was plucked from Now that two Crew RETIREMENT anymore. In a historic first, the water by the recovery Dragon spacecraft have of the the private com- ship Go shortly successfully delivered Program in 2011, NASA pany SpaceX launched two thereafter. Out of an abun- astronauts to the ISS, the astronauts have depended American astronauts into orbit dance of caution, the future once again looks on Russia for rides to the May 30 as part of the Crew astronauts’ departure from bright for American crewed International Space Station Dragon Demo-2 mission. Crew Dragon was delayed spaceflight.

WWW.ASTRONOMY.COM 19 LEFT: Comet NEOWISE’s twin tails spread across the sky over West Texas. Now on its way back to the outer solar system, NEOWISE won’t return for nearly 7,000 years. JAMES LOWREY

eagerly awaited C/2019 Y4 (ATLAS), whose mid-May glow astronomers predicted would be rivaled only by Venus. But on April 11, amateur astronomer Jose de Queiroz snapped a photo that showed the comet breaking up. Hubble images on April 20 and 23 confirmed the comet had fragmented into several pieces — an interesting turn A triple comet surprise of events for researchers, but one that quashed any WHEN IT WAS after its December 8, 2019, chances of ATLAS achiev- 5 DISCOVERED perihelion pass. ing “” status. August 30, 2019, John Noonan of the Fortunately, C/2020 F3 the second-known Lunar and Planetary (NEOWISE) stepped up. It interstellar visitor to our solar Laboratory at the University flared to naked-eye visibility system, Comet 2I/Borisov, of Arizona, Tucson, was part between magnitude 1 and 2 hadn’t yet made its closest of a team that observed after rounding the Sun on pass to the Sun (called peri- Borisov with the Hubble July 3, just over three months Our solar system’s second helion). Unlike 1I/2017 U1 Space Telescope in late after its discovery. The comet identified extrasolar visitor, Comet Borisov, appeared much ‘Oumuamua, which was spot- December and early January. quickly developed a pictur- more cometlike than ‘Oumuamua. ted only after it had already They looked for carbon esque pair of gas and dust This Hubble image was snapped shortly after Borisov made its rounded our star, astrono- monoxide (CO) sublimating, tails that ultimately stretched closest approach to the Sun in mers were able to watch or turning directly from solid more than 30° across the sky December 2019. NASA, ESA AND Borisov before, during, and ice to gas, off the surface. and offered an ideal target D. JEWITT (UCLA) “[CO] sublimates at very low for astrophotographers. . So, if you see NEOWISE spent several , that tells weeks delighting skywatch- you something has been cold ers as the brightest Northern THE COVID-19 PANDEMIC for a very long time,” he says. Hemisphere comet since The coronavirus pandemic impacted astronomy in 2020 in many On Borisov, “there was C/1995 O1 (-Bopp). ways, from major observatories shuttering their scopes to mass more carbon monoxide than “What a great little comet!” transitions to remote work. More than 100 of Earth’s largest tele- there was water, which is astrophotographer John scopes closed at some point during the year. Jet Propulsion pretty much unheard of” for Chumack wrote in an email Laboratory engineers, unable to take their high-performance com- comets in our own solar sys- on July 29 to Astronomy. puters and virtual reality setups out of the lab, drove Curiosity on Mars from home using plastic red-blue 3D glasses to visualize the tem, Noonan says. The By then, the comet was a rover’s complex environment. And scientists launching missions out-of-whack ratio means 4th-magnitude target low in such as Solar Orbiter and faced unique challenges Borisov “very clearly formed the northern sky. “Over the imposed by travel restrictions to reduce the spread of disease. in a system … very different last few weeks, NEOWISE Fall 2020 saw a rash of telescope reopenings as conditions in than our own.” That place put on a nice show for us some locations improved. The Very Energetic Radiation Imaging Telescope Array System in Arizona and the Las Campanas could have been around a red Northern Hemisphere Observatory in Chile had reopened by October 8. — stars smaller observers. Some of my Telescopes at Kitt Peak in Arizona, and Cerro and cooler than our Sun, and astronomy friends in the Pachón and Cerro Tololo in Chile, also began commonplace throughout Southern Hemisphere have reopening at that time. By late October, the the galaxy. now got to glimpse it and

Atacama Large Millimeter/submillimeter E M I

T As Borisov faded from they are reporting it still Array was also readying for reopening S M A

E headlines, comet enthusiasts fading,” he said. and a new round of Pole R D / T

Telescope observers had gone into A R E E

quarantine to prevent carrying the N A H T virus to Antarctica. — A.K., E.B. T U Y A R A

20 ASTRONOMY • FEBRUARY 2021 S First midsized black hole detected FAST FACTS

BLACK HOLES COME in scientists at the Interferometer 4 Stellar-mass black holes: a variety of sizes, ranging Gravitational-wave Observatory (LIGO) a few to 100 solar from a few to billions of times and the partnering Virgo site received the mass of the Sun. Although the first convincing sign: gravitational Intermediate-mass black holes: there is ample evidence for stellar-mass waves that point to the violent birth of 100 to 1 million solar masses and supermassive black holes, there is an intermediate-mass black hole (IMBH). surprisingly little proof of their middle- After spending more than a year scru- Supermassive black holes: weight brethren. But on May 21, 2019, tinizing the signal (called GW190521), millions to billions of solar masses which lasted just a tenth of a second, on September 2, 2020, an international team An IMBH is born of researchers released two papers detail- 85 solar masses, so the larger one firmly ing their results: The gravitational waves falls in the “pair-instability mass gap.” originated halfway across the universe and When most massive stars die, they leave were produced when two hefty black holes behind a black hole. But when a star GW190521 merged to create an IMBH about 142 weighs 130 to 200 solar masses, times the mass of the Sun. Their collision in its core become so energetic they GW150914 also released a stupendous amount of morph into -antielectron pairs, energy, equivalent to roughly eight solar which can’t fully combat gravity. The star GW170608 masses, as gravitational waves. becomes extremely unstable and, after Although this detection confirms that going supernova, leaves nothing behind. IMBHs exist, it also raises questions. The “This event opens more questions GW190814 progenitor black holes weigh in at 66 and than it provides answers,” LIGO member Alan Weinstein, professor of physics at GW190521 signaled the birth of an intermediate- Caltech, said in a press release. “From the mass black hole. But it didn’t sound like a typical perspective of discovery and physics, it’s a “chirp” — it was more like a “bang.” D. FERGUSON, K. JANI, D. SHOEMAKER, P. LAGUNA, GEORGIA TECH, MAYA COLLABORATION very exciting thing.”

The Milky Way does the wave star-forming regions that make up the Wave. That work involved combining observations of the way intervening dust BECAUSE WE ARE EMBEDDED within the and gas makes appear redder with accurate distance 3 Milky Way Galaxy, mapping its large-scale struc- measurements to those stars from ESA’s Gaia spacecraft. ture is challenging. That is especially the case for “Since this effect [reddening] is observable throughout our galactic star-forming regions, huge clouds of gas solar neighborhood, it allowed us to determine the distances and dust whose distance is difficult to measure because to a huge sample of star-forming regions, using the same they aren’t points like single stars. But new work by Harvard technique, for the first time,” Zucker says. “Previous distance University astronomers published January 7, 2020, in Nature techniques were piecemeal, obtained inhomogeneously on a dramatically increased the accuracy of distance measurements cloud-by-cloud basis.” to nearby star-forming regions. It also uncovered something Her technique revealed, to a factor of five times better unexpected: the Radcliffe Wave. than previous measurements, the distances to nearby Nearly 9,000 light-years long and 400 light-years wide, this star-forming regions — and the Radcliffe Wave. “In the snaking line of interconnected star-forming regions rises above future, this will force us to reframe our understanding of star and dips below the plane of our galaxy. It lies less than 500 formation on small scales (i.e., within individual molecular light-years from Earth at its nearest point and connects molec- clouds) in a larger galactic context,” she says. ular clouds in Orion, Taurus, Perseus, Cepheus, and . “Prior to the discovery of the Radcliffe Wave, star-forming regions were studied in relative isolation. The Radcliffe Wave showed that all these regions are connected on the grandest of scales, via tendrils of filamentary gas, which is something we never knew before,” says Catherine Zucker, whose Ph.D. work at Harvard led the effort to pin down distances to the

The Radcliffe Wave (shown in red; the location of our Sun appears in yellow) is a sinuous structure thousands of light-years long and hundreds of light-years wide. It connects several star-forming regions and likely forms the densest part of the spiral arm in which the Sun resides. IMAGE FROM THE WORLDWIDE TELESCOPE, COURTESY OF ALYSSA GOODMAN Researchers think they’ve detected signs of a , phosphine (left), in 1 Venus’ clouds. But that claimed detection has since come under heavy scrutiny. ASTRONOMY: ROEN KELLY; ALMA (ESO/NAOJ/NRAO), GREAVES ET AL. & JCMT (EAST ASIAN OBSERVATORY) Missions to MARS

Astronomers spy phosphine on Venus 2 VENUS IS A SIZZLING others remain skeptical. Chemical com- AS USUAL, world thought by many pounds each have a unique spectrum, or THE RED to be inhospitable to life. fingerprint, that depends on the wave- PLANET Surface temperatures are lengths of light they absorb. Although the has had quite HOPE hot enough to melt lead — almost researchers detected this fingerprint of a year. Not only 900 degrees Fahrenheit (480 degrees phosphine with two independent tele- did NASA’s InSight lander detect Celsius) — while the pressure at scopes at different times, they only saw it hundreds of marsquakes shaking ground level is more than 90 times that at a single wavelength — one that sulfur the planet, but ESA’s of Earth at sea level. But that hasn’t dioxide happens to absorb as well. orbiter found more signs that the stopped some, including Carl , “As a geochemist, I always worry world has several underground from proposing that life could exist about detection from one peak,” says saltwater lakes buried beneath its in the more temperate clouds of our Justin Filiberto of the Lunar and south pole. Perhaps most impor- sister planet. And now, there could be Planetary Institute. “A single line is a tantly, however, 2020 saw three evidence to support that hypothesis — coincidence, not a detection,” adds new spacecraft set forth for the albeit controversial evidence. astrobiologist Kevin Zahnle of NASA Red Planet, taking advantage of a In a paper published September 14 in California. Still once-every-26-months alignment in Nature Astronomy, researchers pre- others are concerned about the quality that shortens the time and distance sented observations of an inexplicable of the noisy data itself, which means required to get from Earth to Mars. surplus of the rancid gas phosphine in many groups are already reanalyzing it. As its first interplanetary mis- the clouds of Venus. On Earth, microbes But if the detection holds up, “it sion, the United Arab Emirates produce most phosphine, though it can demands follow-up,” says Bethany launched an orbiter named al-Amal also be created abiotically under great Ehlmann, a planetary scientist at Caltech (meaning “Hope”) July 19. The craft temperatures and pressures. Measured who was not part of the discovery team. is equipped with both an at a level of some 20 parts per billion, “The top three destinations to look and ultraviolet — the the researchers behind the new paper for life in the solar system are Mars, former meant to investigate dust, say no known geological activity or , and Europa — and now we exotic catalysts — such as lightning or should perhaps add Venus to the list.” — can explain the strength of their observed signal. “We are not claiming we have found life on Venus,” said co-author Sara Stories to watch for in 2021 Seager, an MIT planetary scientist, in a press conference. However, she added, The missions NASA’s Double Because of they can’t explain the phosphine’s . that left Earth Asteroid Redirection technical for Mars in 2020 Test, or DART difficulties and Many find the unexplained biosig- — the UAE’s mission, will launch the ongoing nature, or potential evidence for past Hope, China’s July 22, 2021, to binary coronavirus or present life, tantalizing. However, Tianwen-1, asteroids Didymos pandemic, NASA and NASA’s and Dimorphos. has updated its Alison Klesman and Jake Parks are Perseverance The agency’s target launch date — will all reach spacecraft is scheduled for the James associate editors of Astronomy. They sure the Red Planet in to launch October 16, Webb Space hope 2021 is better than 2020. February 2021. 2021 — the first mission Telescope to to Jupiter’s October 31, 2021. asteroids. 22 ASTRONOMY • FEBRUARY 2021 Three Mars missions from three different countries took advantage of an alignment between Earth and the Red Planet in 2020. The missions will teach us more about Mars’ atmosphere, seek out signs of past and present life, and even cache rock samples for their future return to Earth. NASA/JPL-CALTECH

water, and ice in Mars’ lower atmo- present life. Then the orbiter will enter a sphere and the latter meant to study polar elliptical orbit around Mars. oxygen and carbon monoxide in the There, it will serve as a communica- upper atmosphere. Additionally, the tion relay for the rover and lander, as craft carries a multiband that well as use its seven science instruments can achieve resolutions better than to remotely study Mars’ environment 5 miles (8 kilometers) per pixel. and map its surface. TIANWEN-1 Altogether, Hope aims to paint a more Finally, on July 30, NASA launched comprehensive picture of the Red the Perseverance rover as part of its Mars Planet’s atmosphere. 2020 mission. This car-sized rover, based life once existed in Mars’ Crater. China jumped into the fray next, largely on Curiosity’s design, has ambi- The rover also comes with a few proof- launching an orbiter, lander, and rover tious plans. Equipped with instruments of-concept experiments: an oxygen-pro- trio to Mars July 23. Tianwen-1 (which that can create spatial maps showing the duction device called MOXIE and a means “heavenly questions”) is the elemental and mineralogical com- solar-powered helicopter named country’s first fully homegrown Mars position of rocks, Perseverance . Last but not least, Perseverance

mission. Engineers plan for the orbiter will seek evidence that ancient plans to find, collect, and seal rock and Y L L E K to release the lander/rover combo soil samples that will ultimately be N E O

PERSEVERANCE R after a few months orbiting the returned to Earth for closer inspection : Y M O

Red Planet. It will touch down with sophisticated lab equipment. N O R T S

near in the With all these missions expected to A

: S N O northern hemisphere to reach the Red Planet in February, 2021 I T A R T

seek signs of past or is bound to be a big year for Mars. S U L L I

L L A

Also delayed due The ESA and First light for the Both the Parker The uncrewed to coronavirus, ’ robotic 8.4-meter Simonyi Solar Probe and Artemis I mission, the Indian Luna-25 lander Survey Telescope Solar Orbiter will the first in NASA’s Space Research aims to put Russia at the Vera C. Rubin make flybys of plan to return Organisation’s back on the Moon Observatory in Venus in 2021: humans to the Chandrayaan-3 with an anticipated Chile is expected Parker will make Moon, is scheduled mission, which launch date in in October 2021. two, Solar Orbiter to launch in 2021. comprises a October 2021. will make one. This first mission lander and rover, will combine the is now scheduled new to launch for the System and Moon in late 2021. Orion crew capsule. ROVER begins its mission

24 ASTRONOMY • FEBRUARY 2021 Perseverance is more than just Curiosity’s double — it will hunt for ancient life, cache samples, and pave the way for human explorers. BY JIM BELL

EVERY 10 YEARS, planetary scien- collectively known as Mars Sample tists put their collective minds together Return. Perseverance takes its first driving test on December 17, 2019, in a clean room at NASA’s Jet to develop mission recommendations Now, nine years later, that Propulsion Laboratory in Pasadena, California. for the decade ahead. The most recent of ambitious journey is about to begin. NASA/JPL-CALTECH these decadal surveys, published in 2011, The Mars 2020 mission launched from had a clear top priority for NASA: to Cape Canaveral on July 30, 2020, and is collect samples from the surface of Mars scheduled to land in Jezero Crater on and return them to Earth. February 18, 2021. If all goes well, the The concept of returning samples rover will embark on a mission lasting from Mars has been something of a holy at least a full year (equivalent for planetary scientists. As intrepid to 687 days on Earth). In addition to its as NASA’s previous robotic explorers own explorations, it will also collect and have been, their analyses of the rock and cache samples that will later be returned soil they rove have always been limited to Earth — revealing the mysteries of by the equipment they carry. When you that once-habitable place on Mars. ship a rover to Mars, the cost of every extra ounce is colossal. And rover A clone is born instruments — marvels of engineering In December 2012, just four months though they are — are no substitute for after the Curiosity rover landed a fully equipped laboratory on Earth. on Mars, NASA announced a new That’s why, in the 2011 Decadal wheeled explorer that would address Survey, scientists recommended NASA the top goal of the most recent decadal. Perseverance lifts off on July 30, 2020, atop a design a flagship mission to “collect, It was scheduled to launch during a United Launch Alliance rocket at the document, and package samples for favorable Earth–Mars alignment in Space Launch Complex-41 on Cape Canaveral. future collection and return to Earth.” 2020. This Mars 2020 rover would UNITED LAUNCH ALLIANCE In other words, the community be designed and built by a team at strongly recommended that NASA NASA’s Jet Propulsion Laboratory finally greenlight a set of missions (JPL) in Pasadena, California — a team that included many of the engineers, managers, and others who had built The Perseverance rover is NASA’s follow-up to the Curiosity, as well as previous Mars rov- successful Curiosity rover and will rove Jezero Crater in search of chemical or textural evidence ers , , and . of past microbial life. NASA/JPL-CALTECH To fit NASA’s tight budget and reduce the mission’s complexity, 90 percent of the Mars 2020 rover, cruise stage, and sky crane landing system would be built from spare parts left over from Curiosity. Mars 2020

With social distancing in effect, senior engineers in Southern California conducted their final inspections remotely via a video feed from a at the in Florida. NASA/JPL-CALTECH MARS SAMPLE RETURN

WHILE NO MISSIONS have yet been approved or funded, several space agencies around the world are deep in the planning stages for a Mars sample-return mission. For example, A ROVER’S NASA and the (ESA) are discussing a concept for joint missions that would find, collect, and return the samples cached by the Perseverance rover. And the Chinese National Space Agency is looking into potential robotic sample-return missions as JOURNEY follow-ons to their Tianwen-1 mission, which launched July 23, 2020, and will land a rover in the Utopia Planitia region of Mars in February 2021. The NASA/ESA plan as currently envisioned would involve the launch of two missions in 2026. The first is a dedicated NASA lander carrying an ESA-built “fetch” rover and a small rocket known as the Mars Ascent Vehicle NASA sample ESA Earth (MAV). The fetch rover retrieval lander Return Orbiter 6 would collect the cached rocket rocket ERO travels to sample tubes left by near-Earth orbit Perseverance on Mars’ and releases the samples to Earth. surface and bring them back to the MAV, placing 5 them inside a soccer ball-sized sample cap- ESA’s Earth Return Orbiter (ERO) picks sule. The MAV would up the samples. then launch them into Mars orbit, where an ESA Earth-return orbiter 4 — the second launch of The Mars Ascent Vehicle 2026 — would be waiting (MAV) to capture the sample launches the capsule. That orbiter sample tubes into Mars orbit. would then depart Mars and return to Earth, jetti- soning the capsule for a 3 parachute-assisted land- The fetch rover ing in the Utah desert in places the 2031. — J.B. tubes inside an ascent vehicle. 1 2 Perseverance collects the ESA’s “fetch” rover Midway samples and deposits them carries the tubes to the in tubes on the ground. sample retrieval lander.

ASTRONOMY: ROEN KELLY. SPACECRAFT MODELS: NASA, ESA would thus be a clone, of sorts — looking and weather of its field site. However, a lot like Curiosity on the outside, but Perseverance also has a number of new and costing at least $700 million less than unique objectives. Perhaps the most impor- Curiosity’s $2.8 billion price tag. tant is to seek the signs of ancient life. On the inside, however, the Mars 2020 Ancient means not focusing on any This map shows a hypothetical course that Perseverance might take, based on scenarios plotted rover would sport some entirely new potential living organisms on the surface by mission scientists. The actual route will of course equipment to help it carry out the sample- of Mars today (which are highly unlikely differ, depending on where Perseverance happens caching job the decadal had outlined. to exist, given the harsh radiation, low to touch down within the landing ellipse. The prime mission is to explore Jezero Crater; if the rover survives The mission’s announcement kicked off surface pressure, and frigid ). to tackle an extended mission, it may trek up and out what NASA Associate Administrator for Instead, Perseverance will seek evidence of the crater west to another site, dubbed Midway. ASTRONOMY: ROEN KELLY. BASE MAP IMAGE: ESA/FU-BERLIN; ROVER PATH (PRIME Science John Grunsfeld called “seven of organisms that may have lived billions MISSION): SANJEEV GUPTA AND BRIONY HORGAN; ROVER PATH (EXTENDED MISSION): years of innovation” to develop that of years ago, during a time early in Mars’ RICHARD OTERO, ERISA STILLEY, NATHAN WILLIAMS, ALLEN CHEN, ET AL. equipment, along with some completely history when the surface environment was new tools. In early 2020, nearing the end a lot more like Earth’s. of the seven-year sprint, the rover finally These signs could come in the form of received its name: Perseverance. preserved physical or chemical evidence, ago, back in the Precambrian era, organ- or textures left imprinted on rocks. isms didn’t develop shells or skeletons that In search of ancient life Finding these biomarkers, however, is could easily leave behind fossil remains Many of the Mars 2020 mission’s goals no small task. Geologists have a similar until about 550 million years ago. are similar to those of previous Mars struggle on Earth: Though life began on Among the prime examples of ancient rover missions, like studying the our planet some 3 billion to 4 billion years biomarkers on Earth are stromatolites,

26 ASTRONOMY • FEBRUARY 2021 Delta Delta remnants Delta surface

Delta Crater base rim Western Eastern landing site landing site Lake margin Jezero Crater landing ellipse

Crater floor

N

W

Prime mission Extended mission

2 miles

3 kilometers

which are rock and mineral structures geological or geochemical processes. built up by coordinated groups of simple Rather, samples must often be taken back single-celled organisms, especially cya- into sophisticated laboratories with the nobacteria (formerly called blue-green most advanced equipment that exists. algae). Finding structures like those in This is one of the main motivations ancient rocks on Mars would be an excit- for making Mars 2020 the first step of an ing and potentially profound discovery. international Mars sample-return pro- But definitively confirming these gram. Barring the unambiguous (and structures will be difficult with unlikely) discovery of biomarkers like Perseverance’s toolkit alone. Taking a fossils, the only way to confirm signs of cue from terrestrial geologists, planetary life might be to bring those samples back This reconstructed mosaic view of Jezero Crater’s magnificent river delta from above looks west, out to scientists have realized that equipment to Earth so they can be studied in much the crater rim. The steep slopes of the delta in the used in the field often cannot tease out greater detail. As famously foreground stand up to 350 feet (107 m) above the whether the samples truly provide evi- noted, “extraordinary claims require crater floor. NASA/MSSS/USGS dence of biological action, or only extraordinary evidence.”

WWW.ASTRONOMY.COM 27 uncovered outcrop rocks with interesting sites have to meet certain engi- silica-bearing minerals and nodular neering requirements: close enough to shapes a decade earlier; some researchers the equator to avoid extreme cold; low think these are potential , enough in elevation that a descending as similar features can be found in some rover’s parachute has thick enough air places on Earth. to grasp; and free enough of large rocks, The other three sites all sat within less slopes, and other potential obstacles to than 100 kilometers of each other. Two of avoid crashing into them. them, near the famous dark region Syrtis But sites with large rocks and slopes Major, had abundant deposits of clay and are often some of the most scientifically On September 4, while Perseverance was en route carbonate minerals, potentially indicat- rewarding landscapes. So, clever engi- to Mars, JPL moved the rover’s twin — a full-scale ing an ancient habitable environment. neers from JPL and elsewhere have engineering model dubbed OPTIMISM (Operational The final option was Jezero, a 31-mile- worked to develop more intelligent soft- Perseverance Twin for Integration of Mechanisms and Instruments Sent to Mars) — to its “Mars Yard” wide (50 kilometers) on ware to guide Perseverance’s landing test area. Engineers can test rover commands and the western margin of stage to a touchdown in Jezero Crater. operations using OPTIMISM in an environment that simulates the Red Planet to better understand what that hosts clays, carbonates, and a well- One upgrade makes the descent stage Perseverance is experiencing on Mars. NASA/JPL-CALTECH exposed ancient river delta. more aware of when and where to deploy The workshop participants and Mars its parachute. And once the parachute 2020 science team ultimately recom- is jettisoned and the rover and descent mended Jezero — named after a small stage are in powered retrorocket flight, a Mars 2020 also has a number of new town in the Balkan nation of Bosnia- new hazard-avoidance system helps avoid experiments that are designed to help Herzegovina — as their top choice, and rocks and other large obstacles, guiding engineers develop technology for future NASA officially chose the site as the win- the rover to a height of about 25 feet robotic and human Mars missions. For ner in November 2018. (7.6 meters) over a safe landing site. example, the rover carries a device Jezero will be among the most chal- Then, the sky crane system — pioneered designed to extract small amounts of lenging martian terrains that NASA by Curiosity — lowers the rover to the oxygen (O2) by splitting carbon dioxide has yet attempted to land on. All rover ground via cables for a soft touchdown. (CO2) molecules with electricity. Larger systems based on this technology could Jezero will be among the most challenging generate oxygen for future human crews on Mars. martian terrains that NASA has yet Perhaps Perseverance’s most famous attempted to land on. tech demo is a small four-blade helicop- ter drone named Ingenuity. Early in the mission, engineers will program it to conduct three to five test flights to learn The experimental helicopter drone more about operating drones on Mars. Ingenuity will become the first On future missions, such drones could aircraft to take powered flight on another world. Though it won’t be serve as scouts or sample delivery able to wander far — it will stay systems. less than 0.6 mile (1 km) from the Perseverance rover to remain in wireless communication (right) — Choosing a target future drones could serve as more From 2014 to 2018, NASA and the plane- capable scouts. At left, Ingenuity receives its final inspection at the tary science community carefully studied Kennedy Space Center in Florida options for where to land Perseverance. before being mounted to Perseverance for its journey Just as for previous NASA rover mis- to Mars. NASA/JPL-CALTECH sions, a series of open community work- shops brought together scientists, JPL mission engineers, technology experts, and even members of the general public to discuss and debate which site would offer the best chance of accomplishing the mission’s goals. By the time of the fourth workshop in October 2018, the competition had boiled down to four sites. One option was a return to the in Crater, where the Spirit rover had

28 ASTRONOMY • FEBRUARY 2021 A crater to explore When Perseverance takes in the land- scape inside Jezero Crater for the first time, it will send back images that show the hills of the crater rim rising 2000 feet above the crater floor. If the rover lands close enough to it, early images could also show the 150- to 350-foot-tall edge of one of the most exciting aspects of Jezero: its beautiful western river delta. On Earth, deltas are fan-shaped splays of sediments where rivers gently deposit sand and silt, forming layers of sand- stone and mudstone that can trap and preserve organic materials. Jezero Crater preserves several deltas along its inner In the spring of 2020, as the COVID-19 pandemic took hold around the world, mission staff persevered and rim, showing that it was clearly a shallow adapted to working from home in the runup to the Mars 2020 launch on July 17. Clockwise from upper left: crater lake sometime early in Mars’ his- lead mobility systems engineer Rich Rieber (with son Ben); deputy project scientist Katie Stack Morgan; mission system verification and validation supervisor Ruth Fragoso; mission design and navigation manager tory. If life emerged on Mars long ago, Fernando Abilleira (below mission logo); staff assistant Monica Hopper; systems engineer Heather Bottom; evidence of it might be preserved in project chief engineer Adam Steltzner; guidance and control systems engineer Swati Mohan; Entry, Descent those delta sediments. and Landing phase lead Al Chen (with son Max); project manager John McNamee; and Entry, Descent and Landing systems engineer Cj Giovingo. NASA/JPL-CALTECH What that lake looked like billions of years ago remains unknown, but there are many possibilities. Perhaps waves were lapping at its shores, around what is A major goal of the mission is to drive size of the grain particles, and how now the crater rim. Or, if the climate was the rover up to and perhaps even onto quickly the sediment builds up. The rover too cold for surface water, Jezero may that delta, to search for geologic, miner- team could try to systematically explore have been a vast frozen expanse, with all alogic, and chemical evidence of its past the equivalent of these different zones on the river and delta-building action hap- environs. On Earth, different kinds of Jezero. This strategy could maximize the pening below. It’s tempting to speculate, of life can appear in different areas chances of finding regions where poten- but instead of making wild guesses, the of a river delta depending on the speed of tial biosignatures might be preserved. best recourse is to go there and find out. the water that deposits the sediment, the After exploring and sampling the delta, the team might drive the rover to the foothills at the boundary of the crater floor and rim, where orbital measure- ments show a “bathtub ring” of clay and carbonate minerals — indicators of a past watery environment that dried out as the lake waters receded. From there, the team might drive the rover up the crater rim — charting a course along the safest slopes — to more closely explore the orig- inal ancient rocks from which the delta sediments originated. If the rover team can successfully get Perseverance completely out of Jezero Crater, just 10 miles (16 kilometers) beyond the western rim lies one of the rejected landing sites, dubbed Midway. It’s also rich with ancient clay and car- bonates, but many of those mineral deposits could have been created by groundwater coursing through the rocks, rather than surface water. The chance to explore a very different, but also poten- tially once very habitable, ancient mar- tian environment as part of an extended mission is an exciting prospect.

WWW.ASTRONOMY.COM 29 PERSEVERANCE’S TOOLKIT Caching the samples Of course, Perseverance’s scientific legacy will also depend on the samples it NASA SELECTED PERSEVERANCE’S scientific payload of six instrument systems in collects for return to Earth. To perform a competition between dozens of proposals that researchers submitted in 2014. The this task, the rover’s designers carved winners include three instruments on the rover’s mast: a pair of panoramic, zoomable out a significant amount of space for the 3D cameras called Mastcam-Z; a camera and spectrometer called SuperCam that zaps rocks and soil with a laser to analyze their chemical makeup; and a weather- Sampling and Caching Subsystem (SCS). monitoring station called the Mars Environmental Dynamics Analyzer (MEDA). For the The SCS drill, mounted on the rover’s most part, these are enhanced versions of systems on the Curiosity rover. However, in arm, will take core samples of martian a first, SuperCam includes a high-fidelity microphone designed to record sounds on rock and soil. Its carousel of bits includes Mars — either from the instrument and other rover subsystems, or potentially from the six bits for drilling rock core samples, winds of Mars itself. The rover carries three new science investigations as well. A ground-penetrating one “regolith” bit for collecting soil, and radar system called the Radar Imager for Mars’ Subsurface Exploration (RIMFAX) will two abrading bits for grinding rocks probe underground layers of rock — and potentially water ice. The Planetary or other surfaces for analysis with the Instrument for X-ray Lithochemistry (PIXL) will analyze samples on microscopic rover’s instruments. There’s also a tool scales by focusing a beam of X-rays and taking images of the resulting glow. And an that can blow puffs of nitrogen gas onto instrument called Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) will put samples under a magnifying glass, a sample to remove dust or drill tailings. so to speak, with a microscopic imaging subsystem called Wide Angle Topographic The rover also houses a tiny robotic Sensor for Operations and eNgineering (WATSON). Together, the pair of devices will arm that can capture samples delivered use an ultraviolet laser and spectrometer to search for biomarkers in organics and into the rover’s body, document them, minerals. PIXL, SHERLOC, and WATSON are all mounted on the rover’s hefty robotic seal them in titanium tubes, and then arm; RIMFAX is mounted to the rover’s lower aft deck. In addition to its science instruments, Perseverance is outfitted with engineering- drop them onto the surface for later col- focused cameras and other subsystems. These include cameras for basic navigation, lection and return to Earth. Perseverance as well as front- and rear-mounted cameras for avoiding hazards. There are also seven is carrying a total of 43 of these dry-erase- simple, largely “off-the-shelf” cameras mounted on the rover and the spacecraft stages marker-sized tubes to Jezero. During the that will carry it to the surface. These will record images and video of the landing pro- prime mission, the science team hopes to cess. And, for the first time, there will be sound to go with it — a microphone will be recording audio during the landing. In all, Perseverance, its descent stage, and the fill up to 38 of them with the most com- Ingenuity helicopter are loaded with 25 cameras, making it the most photo-capable pelling and potentially revealing rock spacecraft ever sent to the Red Planet. — J.B. and soil samples as possible. However, the remaining five are just as critical: They are specifically designed to provide “witness samples” that charac- SuperCam terize any organic or other chemical

Mastcam-Z

WATSON SHERLOC MEDA

Rear

RIMFAX

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MOXIE Front HazCams

NASA/JPL-CALTECH; ASTRONOMY: ROEN KELLY

30 ASTRONOMY • FEBRUARY 2021 contaminants that might have been brought to Mars from Earth, despite the HITTING THE MARK team’s best efforts at sterilizing the sam- MARYLAND Baltimore ple tubes. Instead of being filled with WV samples, they will go through a full “mock coring” process and be handled 2020 2022 ExoMars Perseverance and sealed by the rover’s SCS systems just 120 × 19 km 13 × 7 km like the actual samples. This provides a Annapolis way to check whether any organic mate- 2012 Curiosity 2008 19 × 6.5 km rials or other contaminants coming from 100 × 19 km Washington D.C. the rover itself have been able to sneak 2004 Spirit and Opportunity into the actual Mars samples, too. C 150 × 19 km 2018 InSight h 130 × 27 km e s a Ready to rove VIRGINIA p e After several years of design, the rover 1997 Pathfinder a 201 × 71 km k e instruments and subsystems finally 1976 Viking B 280 × 100 km a began taking shape in 2016. Engineers at y JPL assembled the rover in 2019 and put 0 10 20 30 miles it through extensive tests through the 0 25 50 kilometers first half of 2020, simulating the harsh The landing ellipse is the area in which mission planners estimate a lander could touch down — i.e., the thermal conditions on Mars and the margin of error they must account for. Improvements to Perseverance’s landing system make its landing vacuum of space. ellipse smaller and allow engineers to consider targeting more challenging and scientifically interesting The final stages of assembly, testing, terrain. This figure compares the landing ellipses of several Mars missions plotted over the more familiar territory of Washington, D.C. ASTRONOMY: ROEN KELLY, AFTER PAJOLA ET AL. (2019) and installing the craft atop the launch vehicle occurred in the midst of the COVID-19 pandemic. By mid-April, 90 percent of the team at JPL was working from home, but mission-critical personnel were still needed to at the Kennedy Space Center in Florida to prep the rover itself. Following clean protocols was not a challenge for the team, as those are nec- essary for preparing any lander to avoid contaminating the worlds they visit. But they improvised to minimize the number of people needed inside the clean room itself. For instance, the final “walkdown” inspection of the spacecraft — in which experts in each spacecraft system give the rover one last check — took place remotely, with a technician in Florida This aluminum plate bearing the staff of Asclepius — the Greek deity of healing and medicine — was using a smartphone to send a video feed installed on the rover to commemorate the impact of the COVID-19 pandemic and to pay tribute to health to senior engineers at their homes. care workers. NASA/JPL-CALTECH The window for Mars 2020 to actually launch in 2020 ran from July 17 through August 15. If the mission missed that window, it would have had to wait until and issues related to COVID-19. Mars. And many of us are eagerly look- September 2022. The challenges that the Considering the cost overruns that have ing forward to the day when we can see coronavirus presented made the efforts plagued many past NASA flagship-class those rover-collected samples — not just of all involved — including at JPL, missions, a 12-percent overrun could be through the lenses of our sophisticated NASA’s Kennedy Space Center, United considered something of a minor victory. robotic avatar, but with our own human Launch Alliance (the manufacturers of Now, the anticipation is building. eyes. the Atlas V rocket), and other NASA and Who knows what discoveries await us all subcontractor facilities — to make the in Jezero, what new secrets about Mars Jim Bell leads the Mastcam-Z camera team launch window especially impressive. will be revealed by the images and other on the Mars 2020 mission’s Perseverance The ambitious rover did go over its data the rover will collect. Everyone rover. He is an astronomer and planetary original 2012 budget — but only by involved is extremely excited about what scientist at Arizona State University and around 12 percent, partly due to delays we will learn from the rover’s mission on president of The Planetary Society.

WWW.ASTRONOMY.COM 31 Visible to the SKY THIS MONTH 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

This month you’ll find several planets hiding in twilight. Careful FEBRUARY 2021 observers can even follow Venus (pictured here) and Jupiter into Twilight planets delight daylight. JAMIE COOPER

Be ready to catch while. Mars dominates the eve- Morning triad the early morning ning sky and enters Taurus this appearance of four planets: month. Although distant from Mercury, Venus, Jupiter, and Earth and showing a tiny disk, Saturn. They appear in the it will remain in our evening brightening morning twilight skies for a long while yet. AQUILA and some are challenging. Attentive observers may Jupiter passed Saturn last catch Mercury February 1 in Nunki Kaus December and now stands to bright twilight after sunset. It’s SAGITTARIUS Australis its east. Both gas giants rise a challenging view now, follow- CAPRICORNUS earlier each morning as they ing its greatest eastern elonga- Mercury Saturn increase their elongation from tion late last month. Begin your Jupiter the Sun, preparing for a fine attempt 30 minutes after sunset. 10° spring lineup before dawn. Can you spot the magnitude 0.9 Venus is heading to superior planet 6° high in the western with the Sun and sky? Watch with binoculars for February 20, 30 minutes before sunrise is briefly visible in the dawn 15 to 20 minutes as the sky Looking southeast sky. Mercury is near the end of darkens and Mercury dips Early risers can catch Mercury forming the apex of a triangle with Saturn and its morning apparition. lower. The planet descends Jupiter shortly before sunrise on February 20. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY The evening skies of quickly and 15 minutes before February carry the distant it’s gone, it stands 2° high — luck. Locations with the best a clear view to the west. giants Neptune and Uranus tough to spot at such a faint chance are those with fine Mercury passes through infe- — Neptune is lost quickly in magnitude, but some observers atmospheric transparency rior conjunction February 8 twilight, but Uranus lingers a with clear skies may have good offered by a high altitude and and springs into the dawn sky

32 ASTRONOMY • FEBRUARY 2021 RISING MOON I Lunar strongmen

PROMINENTLY PAIRED CRATERS Atlas and Hercules and Atlas Hercules rule the lunar northeast. Without com- pare in strength, these mythological musclemen have appropriately striking features named after Mare Humboldtianum OBSERVING them. HIGHLIGHT Their chiseled forms seem to pop out on the Atlas 16th, lit by a rising Sun in the lunar sky. Atlas, the MERCURY, SATURN, and JUPITER share the dawn sky one closer to the limb, sports a rough floor and this month. Catch them central peak. Just to the west, Hercules straddles Hercules Februar y 20, forming a the day-night line, the terminator. Over the next triangle a mere 30 minutes few hours, watch the long shadows slowly before sunrise. retreat. The western inner walls face the N brilliant Sun, while their eastern sides remain dark. Return on the 17th to see E the floor of Hercules — surprise! It's a pool of frozen lava with the barest hint The striking Atlas and Hercules craters along with Jupiter — more on of a central peak and a sharp crater just should draw your attention in mid- to late February. CONSOLIDATED LUNAR ATLAS/UA/LPL. off the bull’s-eye. that later. INSET: NASA/GSFC/ASU Neptune makes a brief Each bowl is surrounded by an apron of appearance early in February as debris. Under the low Sun angle, can you tell as it bobs up and down in its orbit around Earth, a binocular object in Aquarius. which one drapes over the other? Researchers we see it from slightly different points of view. It lies less than 20° high once disagree over which formed first. It may help to Astronomers call this apparent nodding motion the sky is dark. The magnitude look with reversed lighting, when the setting of our satellite libration. 7.8 planet lies slightly less than Sun illuminates the craters’ eastern flanks on Any time after First Quarter (the 19th), we’re 2° northeast of Phi (ϕ) Aquarii, March 1, a few days after Full. close to lunar high noon for both Atlas and a dim 4th-magnitude star, on Luna slowly turns its nose up at us beginning Hercules. Without the shadows, Atlas practically February 1. The pair’s angular on the 17th. Key in on the limb northeast of disappears. In contrast, Hercules’s lava lake Hercules and watch the dark floor of Mare stands out well against its neighboring light- separation increases as the Humboldtianum shift out of sight from night to hued crater. Pay close attention — Luna reveals month progresses. By mid- night. The Moon’s axis does not actually tilt — a different face every night. month, the planet is too low to find, and it’s telescopically dis- appointing due to turbulence in our atmosphere muddying the view. It will reappear in the WATCH I A dim, dusty glow morning sky later in the spring. Mars and Uranus begin the WITH NO MAJOR SHOWERS, False dusk month about 6.5° apart in the February is traditionally a quiet constellation Aries the Ram. month for meteors. The average Uranus is only visible with bin- sporadic (random) rate for meteors oculars for most observers. At is seven per hour and there are occa- magnitude 5.8, it may be visible sional fireballs — meteors that break to the naked eye under excep- up and achieve a brilliance of Venus tionally clear sky conditions. It or greater. These are, of course, rare, lies 10.5° south of Hamal, the but worth spending time under a brightest star in Aries. A wax- night sky ready for their appearance. The zodiacal light begins to make ing crescent Moon lies within an appearance during moonless 5° of Uranus on February 17 nights in February, March, and April. and skips next door to sit 4° The evening view of this subtle south of Mars on the 18th. glow, which arises from the meteor- Through a telescope, Uranus itic dust that fills the plane of our displays a fine 3.5"-wide disk solar system, gets better as the with a greenish hue on nights Moonless February evenings are perfect for spotting the glow of the becomes more steeply zodiacal light from a dark location. BARRY BURGESS when stars are not twinkling inclined to the horizon. The first two badly — a sure sign of good weeks of February are favorable, with the Moon in the morning sky. As soon as the Milky Way becomes seeing conditions. visible — arching from high up in Perseus through Orion and toward the southern horizon — look for a Mars shines as a brilliant faint, cone-shaped glow of light reaching up from the western horizon through Pisces, Aries, and into beacon among the faint stars of Taurus at its narrowest. The zodiacal light is never seen from cities or towns, but is visible from country — Continued on page 38 locations with dark skies to the west.

WWW.ASTRONOMY.COM 33

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S BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT www.Astronomy.com/starchart. FEBRUARY 2021

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WWW.ASTRONOMY.COM 35 PATHS OF THE PLANETS

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LAC LYN LYR CVN CYG HER BOÖ Asteroid Amphitrite ene COM reaches opposition Ir GEM February 21 CNC VUL CrB tic) (eclip DEL Sun PEG LEO the SGE h of Pat Eunomia SER EQU CMi AQL SER OPH VIR Celestial equator AQR Asteroid Melpomene SEX reaches opposition Sun on Mercury Mo February 1/2 Saturn the SCT h of HYA Pat CRV CRT Jupiter CAP CMa LIB ANT PsA Venus PYX PUP MIC CrA SGR LUP SCO GRU CEN

Moon phases Dawn Midnight

13 12 11 10 9 8 7 6 5 4 3 2 1

To locate the Moon in the sky, draw a line from the phase shown for the day straight up to the curved blue line. 28 27 26 25 24 23

THE PLANETS Uranus THE PLANETS IN THE SKY IN THEIR ORBITS These illustrations show the size, phase, Arrows show the inner and orientation of each planet and the two planets’ monthly m otions brightest dwarf planets at 0h UT for the dates in the data table at bottom. South is at the top and dots depict the Jupiter Neptune to match the view through a telescope. outer planets’ positions Saturn at midmonth from high above their orbits.

Venus Mars Pluto Mercury Mercury Inferior conjunction is February 8

Mars PLANETS MERCURY VENUS Earth Ceres Date Feb. 28 Feb. 1 Magnitude 0.3 –3.9 Angular size 8.0" 10.1" Venus Illumination 45% 98% Distance (AU) from Earth 0.843 1.652 Distance (AU) from Sun 0.440 0.728 Jupiter (2000.0) 21h01.6m 20h05.0m (2000.0) –16°12' –20°58'

36 ASTRONOMY • FEBRUARY 2021 CAS

LAC PER AND 1 CYG AUR 2 Ganymede TRI Europa

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23 MARS CERES JUPITER SATURN URANUS NEPTUNE PLUTO 24 Feb. 15 Feb. 15 Feb. 28 Feb. 28 Feb. 15 Feb. 15 Feb. 15 0.7 9.3 –2.0 0.6 5.8 7.8 15.1 25 7.0" 0.4" 33.0" 15.4" 3.5" 2.2" 0.1" 26 89% 99% 100% 100% 100% 100% 100% 1.329 3.732 5.972 10.811 20.072 30.831 35.065 27

1.567 2.941 5.076 9.978 19.766 29.926 34.221 28 3h08.4m 0h03.1m 21h14.9m 20h42.5m 2h18.7m 23h22.9m 19h50.3m 19°03' –8°21' –16°34' –18°41' 13°24' –5°09' –22°18' WHEN TO SKY THIS MONTH — Continued from page 33 VIEW THE PLANETS week of the month, but the tiny disk makes them hard to EVENING SKY spot except under optimum Mars (southwest) seeing conditions. Skilled Uranus (southwest) Neptune (west) observers who practiced video capture during last year’s MIDNIGHT opposition can still bring them Mars (west) out if conditions cooperate. MORNING SKY Four planets congregate in Mercury (east) the dawn twilight this month. Venus (east) Some events are difficult to Jupiter (east) catch due to their proximity Saturn (east) to the Sun. For example, on February 6, Venus stands less Although no meteor showers take place in February, keep your eyes on the sky than a Moon’s-width southeast for sporadic meteors, including the occasional fireball. MIKE LEWINSKI of Saturn, but they rise only Venus, on its way to a late half an hour before the Sun. March superior conjunction, Aries, beginning the month at most observers in the U.S. Even at magnitude –3.9, Venus passes 26' due south of Jupiter magnitude 0.5 and dipping to The lack of albedo features is will be hard to see. Saturn is February 11. They’re located just 0.9 by the end of February. The apparent during mid-February, not visible at a much dimmer 10.5° east of the Sun. Jupiter Red Planet this month has as desert regions transit the magnitude of 0.6. shines at magnitude –2; the pair competition from Aldebaran, martian disk during our eve- the brightest star in Taurus the nings. Solis Lacus and Sinus Between February 1 and 28, Mars retreats Bull, which glows at magnitude Meridiani, two distinctive dark 0.3 0.8. Can you tell which night features, are on view in the last nearly 0.3 AU from Earth. they are both equal brightness? Mars moves into Taurus February 23 and ends the COMET SEARCH I Challenge versus chance month nearly 14° northwest of Aldebaran and nicely placed COMET ENTHUSIASTS are used to excitement, disappointment, and satisfaction all in one month. No about 3° southwest of the con- one can be sure which it will be this spring. As Earth circles the inner solar system, some comets coin- trasting blue stars of the cidentally arc behind the Sun, popping into visibility with only three months’ notice before they peak, (M45). missing our publication deadline. The Red Planet presents a Surprising us twice since its discovery, 17P/ has outburst to 2nd magnitude. Cruising in front of tiny disk through telescopes as the circlet of Pisces, will it shine anew? Meanwhile, as 141P/Machholz 2 sails from to Orion, its last its distance from Earth contin- fragment might flare up to ues to increase apace. Its 10th magnitude for a final show. Comet 88P/Howell gibbous phase is a distinctive With great but not absolute confidence, we expect Comet 90 percent lit. On February 1, b 88P/Howell to present a challenge N it’s already 1.2 astronomical ¡ e units from Earth (1 astronomi- for an 8-inch scope under a dark f cal unit, or AU, is the average sky. Once you’ve confirmed the starfield is right, pump up the PISCES Earth-Sun distance). That dis- h a magnification to about 200x. Get Path of tance increases to nearly Mar 2 1.5 AU by February 28. The comfortable, dark adapt as much 25 Comet Howell as possible, and patiently scan for E disk’s angular size shrinks CETUS 20 a very small fuzz — picture a from nearly 8" to 6.4" over the 15 13th-magnitude elliptical galaxy. course of the month. 10 Tapping the scope gently can 5 Features so familiar during leverage our eyes’ low-light Feb 1 AQUARIUS q Mars’ opposition late last year motion-detector system, while NGC 157 Neptune are now tougher to spot. also suppressing “phantom s1 During the first five days of f galaxies” produced by a noisy d February, the darkest — visual cortex. 2° Syrtis Major — swings into The best comet hunting this A challenging 88P/Howell skims through Pisces on its way from Aquarius to view in the evening between month is during the moonless first Cetus this month. The location of Neptune is shown on February 7. Should sunset and local midnight for half of February. they flare up, 17P/Holmes is west of this field and 141P/Machholz 2 is east.

38 ASTRONOMY LOCATING ASTEROIDS I Buzzing the Crab

IT’S TWO-FOR-ONE asteroids this month. Floating only one Bull crossing field apart, 18 Melpomene and 60 Echo track across southern Cancer. The celestial crab is well placed one-third of the way up the eastern sky once darkness sets in. This aquatic constellation Betelgeuse ORION Aldebaran Pleiades boasts the splashy (M44); start with this show- piece, then shift a few degrees south to Alpha (α) Cancri and M67. Mars Sirius TAURUS From the 5th to the 8th, magnitude 10 Echo shares the CANIS medium-power field with the well-studied cluster M67. MAJOR Hamal Melpomene is just over 1° to the north and is a bit brighter at ARIES magnitude 9.5. Crank the power to the max on M67 and test your limiting magnitude against the chart in the Royal Astronomy Uranus Menkar Society of Canada’s Observer's Handbook or one generated online at the American Association of Observers’ website, ERIDANUS www.aavso.org. Until much brighter arrives in spring, we must be CETUS meticulous in our identification of these main-belt asteroids. Starhop carefully, sketch a field in the expected area, then come 10° back a night or two later to see which dot has moved. The orange star FX Cancri varies only slightly from magnitude 6.7, making a nice reference in the same field. February 28, 8 P.M. Looking southwest Thanks to the longer nights of February, you might be able to see these small worlds move slightly over a four-hour session. Mars crosses into Taurus February 23 and ends the month beneath the Pleiades (M45). Uranus floats nearby in Aries and is visible with binoculars Double feature or a telescope. may be seen in binoculars planets’ visibility improves N j a 20 minutes or so before sunrise, each consecutive morning. but will be very challenging. Try on the morning of M44 Observers, be very cautious — Saturday, February 20, to spot 2 you can easily lose track of time all three planets in a triangle: b c CANCER as the Sun comes up. Protect Saturn and Mercury rise Mar 2 yourself by setting an alarm to together 4.4° apart around E 25 go off several minutes before 5:40 A.M. local time, followed Path of 20 / 15 sunrise. Never scan the skies by Jupiter 7° east of Saturn Melpomene 10 Mar 2 after sunrise, because an acci- about 22 minutes later. 5 FX Feb 1 25 20 dental view of the Sun through Mercury and Saturn match _ 15 M67 10 binoculars will cause lasting in magnitude February 22, 5 g Feb 1 Path of Echo damage to your eyes! when they stand almost 5° high Tarf Observers with clear, trans- 40 minutes before sunrise. 2° parent daytime skies and an Jupiter stands less than 1° high, accurately aligned telescope but its brilliance makes it more Asteroids Melpomene and Echo travel together this month through on February 11 can use their easily visible. It lies about Cancer. Close by is the sparkling Beehive Cluster (M44). go-to device to find Venus and 5° east (lower left) of Mercury, Jupiter in daylight. while Saturn stands 4° to On February 15, Saturn Mercury’s southwest (right). — all three planets are cur- Saturn are full. Jupiter spans and Mercury rise together in The triangle formed by rently on the far side of the 33" and is accompanied by its the eastern sky, but remain this trio of planets flattens as Sun. Mercury is closest to four , just vis- difficult objects due to their Mercury drops in declination Earth at 0.85 AU, while Jupiter ible in the shimmering haze. relative faintness in twilight. in late February, brightening as is at 6 AU and Saturn is a dis- Saturn’s disk is 15" wide and its By February 18, they stand it does so. On February 28, it tant 10.8 AU away. bright spans 34" at roughly 3° high 45 minutes shines at magnitude 0.3 and If you’re able to swing a its widest. before sunrise. Mercury has stands only 3° west of Jupiter, telescope towards these plan- brightened to magnitude 1.2, with Saturn 5.5° to Mercury’s ets, you’re in for a visual — Martin Ratcliffe is a while Saturn remains easier west. It’s amazing to get this though short-lived — treat, planetarium professional and at magnitude 0.6. The two view across the solar system since twilight is advancing enjoys observing from Wichita, quickly. Mercury displays a Kansas. Alister Ling, who GET DAILY UPDATES ON YOUR NIGHT SKY AT 46-percent-lit disk spanning lives in Edmonton, Alberta, is a www.Astronomy.com/skythisweek. 8", whereas both Jupiter and longtime watcher of the skies.

WWW.ASTRONOMY.COM 39 Corona light Missed last year’s annular eclipse? We’ve got you covered with some of the best shots out there. BY JAY PASACHOFF

BACKGROUND: The Mango Education Group experienced annularity during clear weather from Dehradun, which is the most populous city in the Indian state of Uttarakhand. That fortunate weather allowed them to capture this crisp shot of the thin circle created by the Sun’s disk stretching out just beyond the Moon’s silhouette. HARINDRA BARAIYA (WILDLIFE INSTITUTE OF INDIA/MANGO ASTRONOMY CLUB); IMAGE FORWARDED BY STEPHEN INBANATHAN (AMERICAN COLLEGE IN MADURAI)

RIGHT: On June 21, the Moon was relatively far from Earth thanks to its slightly elliptical orbit. That meant its angular size was smaller than usual. Therefore, it couldn’t fully block the solar disk when the Sun, Moon, and Earth aligned, or entered , as shown in this artist’s illustration. ASTRONOMY: ROEN KELLY AFTER ERNEST T. (NASA’S SCIENTIFIC VISUALIZATION STUDIO)

40 ASTRONOMY he wild year of 2020 otherwise. And although I don’t keep in boasted two solar eclipses: constant contact with every one of them, an annular eclipse on when an eclipse passes overhead anywhere in June 21 and a total solar the world, I have a good chance of hearing eclipse on December 14. from some of my old friends who are eager Travel restrictions pre- to share their new pictures. vented North Americans, At the time of this writing, the next solar Tas well as many ot hers in the Western eclipse to be seen from Earth will be total, Hemisphere, from viewing the path of annu- with its peak occurring near the border of larity that stretched from Africa through the Argentina and Chile on December 14, 2020. Middle East to Pakistan, India, mainland Be sure to keep an eye out for images of China, and Taiwan. Fortunately, local eclipse December’s total in future issues viewers who managed to get beneath the of Astronomy. Corona Moon’s shadow captured wonderful images Meanwhile, the next annular eclipse will of the breathtaking event. be on June 10, 2021. Its path will trek from The following is a smattering of shots southern Canada over the North Pole and from last June’s annular eclipse, which I down to the Russian Far East. Observers in monitored into the wee hours of the morn- the northeastern will be happy ing with the help of email, the web, and to learn that partial phases of this annular livestreams from the Middle East and Asia. eclipse will be visible to them in the early My decades-long interest in eclipses, and the morning. So, make sure to get your filtered resulting expeditions I have taken to view solar eclipse glasses now, available at them, have allowed me to meet many fasci- MyScienceShop.com. nating people whom I never would have And don’t forget: Share what you see!

A RINGED ECLIPSE

The word annular comes from annulus, which means “ring.” So, when the Moon is just far enough away from Earth that it leaves the outer perimeter of the Sun’s disk unobscured, the result is often referred to as a “ring-of-fire” eclipse. At maximum coverage, this outer band of is up to a few percent of the solar disk’s diameter. So, technically, it could be called a “ring-of-photosphere” or a “ring-of-sunlight” eclipse. The term “ring-of-fire” has murky origins dating back at least 150 years, but its modern usage in reference to annular eclipses has been around for at least a few decades, when it started popping up in various publications. However, “ring-of-fire” is somewhat misleading ter- minology, and it is disliked by many professional and amateur astronomers, or so-called umbraphiles (the umbra is the dark part of a shadow). Contrary to common conception, there is no chemical fire on the Sun. Rather, we owe the warmth and light we receive from the Sun to the clean thermonuclear fusion of hydrogen gas safely occurring some 93 million miles (150 million kilometers) away.

IMAGES: JAY PASACHOFF. COMPOSITE: MUZHOU LU

WWW.ASTRONOMY.COM 41 1

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The Moon’s shadow 1 first touched the Republic of Congo during the June 21 annular eclipse. After it departed Africa, it went through the Middle East, then passed through southern Pakistan, northern India, mainland China, and Taiwan before vanishing southeast of Guam. The annular eclipse path, which stretched 9,058 miles (14,578 km), was just 13 miles (21 km) wide and maximum eclipse (99 percent) lasted only 38 seconds. MICHAEL ZEILER AN UNFILTERED VIEW LEADS TO A REVISION The path of annularity also 2 grazed Saudi Arabia, resulting in a partial eclipse for many. The June 21 annular address to remember: eclipses.info. The working Abouazza Elhamdi of the Astronomy eclipse also group also serves as a clearinghouse for profes- and Physics Department of King traced a path sionals pursuing international eclipse expeditions, Saud University captured this through coordinating such as visas, customs, and sequence of partial phases in the the shipping of equipment. early morning from Riyadh. I am Pakistan, where working with Abouazza, Marcos the cloud-cover For these images, Zia and Kentrianakis forwent Peñaloza-Murillo of Venezuela, and forecast was filters in order to capture detailed views of Baily’s Michael Roman of England to not as favorable beads, which occur when sunlight peeks through analyze how eclipse darkening as in the lower valleys along the lunar limb. This allowed them to impacts the local temperature Arabian Peninsula. successfully detect the solar , and and humidity in desert climates. Fortunately, it turned even the inner solar corona. ABOUAZZA ELMHAMDI out to be very clear. Prior imaging of Baily’s beads taken during pre- LEFT: Unlike central Saudi From Sukkur — a city in vious total solar eclipses led to discussions 3 Arabia, observers in Izki, Oman, the Pakistani province of Sindh — Talha Moon Zia, between me, Xavier Jubier, and Ernest T. Wright of did see annularity. Alaa Ibrahim and who is a research astronomer at Pakistan’s NASA’s Scientific Visualization Studio. We con- Zach Ioannou of the Astronomy National Center for Big Data and Cloud Computing/ cluded that the IAU’s nominal solar diameter — the Group in the Department of Physics at Sultan Qaboos University NED University of Engineering & Technology, defined size of the Sun’s photosphere, which is captured a series of images with obtained these wonderful unfiltered views of the used for predicting the length of eclipse totalities the aid of a hydrogen-alpha filter, annular eclipse. The shots were created by stacking down to a fraction of a second — needed a minor including this single short exposure. several short-exposure images and were taken revision. By comparing our observations to simula- RIGHT: Made by stacking 210 under the guidance of Michael Kentrianakis, the tions by Jubier of the expected Baily’s beads for this images, this view reveals solar eclipse, which were based on high-resolution 3D prominences, or bright tendrils of former project manager of the American chromospheric-temperature plasma Astronomical Society’s 2017 U.S. eclipse efforts and mapping of the lunar surface obtained by NASA’s that extend into the corona. During a member of our International Lunar Reconnaissance Orbiter and the the event, the observers tracked Astronomical Union’s (IAU) Working Japanese Kaguya mission, we found changes in ambient temperature Group on Solar Eclipses. our suspicions were confirmed. and humidity. Before the eclipse, Our IAU group focuses on being Zia’s observations, as well as it was 113 degrees Fahrenheit (45 degrees Celsius), which caused a central resource for anyone Jubier’s simulations, show the some equipment to overheat. But as looking to find out more about true size of the Sun’s photo- the Moon blotted out most of the past or upcoming solar eclipses. sphere is slightly larger than Sun’s disk, the temperature dropped To do this, we maintain a web- previously thought. down to 90 F (32 C). LEFT: A.I. IBRAHIM. site at the easiest possible RIGHT: A.I. IBRAHIM/I.A. ALSHAIKH BOTH IMAGES: NCBC-NEDUET 4

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Rafay Kazmi, a student 4 at Williams College in Williamstown, Massachusetts, observed a partial eclipse from his home in Islamabad, Pakistan. Here, he and his sister are seen viewing the eclipse through special solar filters, one of thousands left over from the 2017 Great American Eclipse and available through Astronomers Without Borders. RAFAY KAZMI

Clouds only served to add 5 mystique to this view of the eclipse from the city of Sirsa in the northern Indian state of Haryana, taken by Neelam and Ajay Talwar. NEELAM & AJAY TALWAR

This series of images, showing 6 the partial eclipse as seen from Coimbatore, a city in the south Indian state of Tamil Nadu, was captured by members of the Mango Astronomy Club. OBULI CHANDRAN

The Talwar team also captured 7 this series of images tracking the of the annular eclipse over Sirsa. Even through the clouds, one can identify Baily’s beads, the solar chromosphere, and, perhaps, even the solar corona. NEELAM & AJAY TALWAR

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WWW.ASTRONOMY.COM 43 8 ECLIPSE RESOURCES

Many observers who were unable to personally see the annular eclipse dim the skies during the daytime instead opted to monitor images and livestreams of the event aired during the middle of their local night — an option not available to eclipse enthusiasts just a few decades ago. Now, worldwide communication and online eclipse- mapping tools, like those from Xavier Jubier of France (http://xjubier.free.fr/ase2020map) and retired astro- physicist Fred Espenak (EclipseWise.com), provide detailed eclipse data for any location on Earth. Additionally, cartographer Michael Zeiler of New Mexico has meticulously created high-quality eclipse maps, while cloudiness statistics over the decades have been gleaned and put into context by Jay Anderson of Canada. (Anderson and I jointly authored the Peterson Field Guide to Weather, which is being published in summer 2021.) All of these resources are linked on the website for the International Astronomical Union’s Working Group on Solar Eclipses (http://eclipses.info), which I chair. Additionally, observations of the 75 or so solar eclipses I worked on in the past are posted to the Williams College Eclipse Expeditions website (https://sites. williams.edu/eclipse).

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Amateur astronomer Zhou 8 Guanhuai (left), with whom I have previously corresponded about earlier eclipses, sent an image of the partial eclipse (right) as seen from Jinan, Shandong province, China. Here, the partial eclipse reached its greatest coverage at 15:55 local time with 67 percent of the Sun’s disk blocked. ZHOU GUANHUAI

Due to travel restrictions 9 related to the COVID-19 pandemic, I was unable to venture to Europe. This image, however, came from Thessoliniki, Greece. It was captured by Aris Voulgaris, with whom I closely work on total solar eclipses. ARIS VOULGARIS

Near the end of the path 10 of annularity in Guam, the eclipse was visible with 97 percent coverage, as seen in this eerie shot. The path of annularity continued about 50 miles (80 km) out to sea — briefly tempting me to fly to the U.S. territory for a quarantined glimpse from a boat. DEAN PATRICK SERVITO

44 ASTRONOMY • FEBRUARY 2021 11

A camera mounted to the 11 o utside of the International Space Station captured this shot of the Moon’s shadow racing across Earth (near the border of Kazakhstan and China) during the June 21 annular eclipse. In the foreground, a Japanese cargo spacecraft is visible. NASA/ISS EXPEDITION 63

The X-ray telescope on 12 the Japanese Hinode spacecraft captured this series of shots, which have been rescaled and colored, showing the Moon blocking the Sun’s disk during the 12 June eclipse. Astronomer Taro Sakao of the Japan Aerospace Exploration Agency (JAXA) took 13 advantage of Hinode’s vantage point to observe how plasma moves within the high-speed solar wind stream, using the lunar Jay Pasachoff is Field silhouette for calibration of stray light. JAXA/HINODE (THANKS TO ALPHONSE Memorial Professor of STERLING OF NASA’S MARSHALL SPACE FLIGHT Astronomy at Williams CENTER, AND KATHY REEVES AND LUCAS GULIANO OF THE HARVARD-SMITHSONIAN CENTER FOR College in Williamstown, ASTROPHYSICS) Massachusetts, and The passage of the Moon’s chair of the International 13 shadow across Earth’s Astronomical Union’s surface was also tracked by the European Meteosat-8 and the Working Group on Solar Japanese Himawari-8 spacecraft. Eclipses. He has worked Here we see a Meteosat view of on 75 solar eclipses and Moon’s shadow over northeast Africa, the Red Sea, and the written about the Sun for Arabian Peninsula. The next Astronomy since its very annular solar eclipse will occur June 10, 2021. EUMETSAT first issue. His research is sponsored by the NSF.

WWW.ASTRONOMY.COM 45 With three Messier objects and loads of other bright targets, the Charioteer has a lot to offer. // BY MICHAEL E. BAKICH

he constellation N Auriga (pronounced or-EYE-guh) the T NGC 2126 Charioteer, a star pattern known by this name for several thousand years, is easy to recognize primarily because of its brightest star, _ AURIGA NGC 1664 Capella (Alpha [α] Aurigae). ¡ This luminary is the sixth- ` brightest nighttime star and l shines with an intense yel- NGC 2281 d c low light. The constellation’s h Beta star, magnitude 1.9 o Menkalinan, is 40th brightest. i NGC 1857 + t The Charioteer is visible E p m in the evening from mid- e NGC 1778 M38 autumn through winter in NGC 1907 the Northern Hemisphere. NGC 1931 IC 405 f Its center lies at R.A. 6h01m M37 M36 IC 410 and Dec. 42° north. Auriga r NGC 1893 ranks 21st in size out of the 29 88 , covering 26 657.44 square degrees g (1.59 percent) of the sky. Its 5° ` size is a bit of a hindrance to its visibility, however. It lies in ASTRONOMY: RICHARD TALCOTT AND ROEN KELLY the middle of the constella- midnight. With respect to Auriga contains three its borders for you to point a tion ladder (43rd) in terms of visibility, anyone living north Messier objects (all open clus- telescope at. Good luck! overall brightness. of latitude 34° south can see ters) and several other open The best date each year to the entire figure at some time clusters and emission nebulae. Michael E. Bakich is a see Auriga is December 21, during the year. And it’s com- Because it lies along the Milky contributing editor of Astronomy when it stands opposite the pletely invisible only to those Way, it doesn’t contain any who enjoys slowly moving his Sun in the sky and reaches who live at latitudes south of galaxies. As you can see, how- telescope through a single its highest point at local 62° south. ever, lots of targets lie within constellation.

Open cluster NGC NGC 1664 is an 1 2281 glows at 2 attractive open magnitude 5.4 and cluster 2° west of measures 14' across. magnitude 3.0 Epsilon It lies 0.8° south- (ε) Aurigae. It glows at southwest of magnitude magnitude 7.6 and 5.0 Psi7 (ψ7) Aurigae. spans 18'. A 4-inch Through a 4-inch scope scope at 100x reveals at 100x, you’ll spot two three dozen stars. The dozen stars. Four stars background star field is forming a parallelogram rich, but you’ll have no sit at the center of the trouble picking out the cluster. ANTHONY AYIOMAMITIS cluster. JASPAL CHADHA

46 ASTRONOMY • FEBRUARY 2021 NGC 1778 is a magnitude 7.7 open Barnard 29 is a dark nebula that 3 cluster with a diameter of 8'. You’ll 4 lies 2.4° southeast of magnitude find it 2° east-southeast of magnitude 2.7 Iota (ι) Aurigae. Through a 12-inch 5.1 Omega (ω) Aurigae. Through a scope, B29 appears as a gray, mottled 4-inch scope, you’ll see two dozen region that blends gradually into its stars unevenly spread across this starry surroundings. The darkest area cluster’s face. Double the aperture appears 15' across. MARTIN C. GERMANO The Flaming Star Nebula (IC 405) appears as a dim 30' by 20' wisp of light. to 8 inches, and you’ll raise that star 5 To observe it, first find AE Aurigae, which lies 4.2° east-northeast of Iota. count to 50. MARTIN C. GERMANO Through a 6-inch scope, the nebula appears triangular. ALISTAIR SYMON

Open cluster NGC 1857 sits 0.8° IC 410 is a large (40' by 30') emis- NGC 1907 is a magnitude 8.2 open The Starfish Cluster (M38) is 6 south-southeast of magnitude 4.7 7 sion nebula 2.4° west-northwest 8 cluster that spans 6'. A 4-inch 9 the westernmost and faintest Lambda (λ) Aurigae. It glows at mag- of magnitude 4.7 Chi (χ) Aurigae. The scope at 100x shows about a dozen (magnitude 6.4) of the three Messier nitude 7.0 and measures 5'. Through nebulosity glows brightest in an area stars. Use a low-power eyepiece and open clusters in this constellation. an 8-inch scope, you’ll see 25 stars 5' in diameter on the northwestern you’ll sweep up an even-brighter open A 4-inch scope will reveal three around 13th magnitude. The exception edge. Use a 12-inch scope with an cluster: M38, 0.5° to the north- dozen stars in an area 20' across. is 57903, a magnitude 7.4 yellow Oxygen-III filter and this object will northeast. MARTIN C. GERMANO ANTHONY AYIOMAMITIS star at the center. MARTIN C. GERMANO knock your socks off. MARK HANSON

Emission nebula NGC 1931 The Pinwheel Cluster (M36) is The Salt and Pepper Cluster NGC 2126 lies midway between 10 sits 0.8° east-southeast of 11 the least spectacular of the 12 (M37) displays an even 13 magnitude 1.9 Menkalinan (Beta magnitude 5.1 Phi (ϕ) Aurigae. An Messier trio in Auriga. At magnitude distribution of stars — a rarity in open [β] Aurigae) and magnitude 3.7 Delta 8-inch scope at 200x shows the 6.0, however, it still outshines 99.99 clusters. A 3-inch scope reveals 50 (δ) Aurigae. It glows at magnitude nebula, which spans 4'. It orients percent of the sky’s star clusters. stars. Through a 10-inch scope, you’ll 10.2 and spans 6'. Through a 6-inch northeast to southwest and shows Through a 4-inch scope, you’ll see count 200, and a 16-inch will reveal telescope, you’ll see about 20 stars. non-uniform brightness across its several dozen stars strewn across an 500. M37 glows at magnitude 5.6 and The magnitude 6.0 star SAO 40801 face. AL AND ANDY FERAYOMI/ADAM BLOCK/NOAO/ area 12' wide. ANTHONY AYIOMAMITIS is 20' across. ANTHONY AYIOMAMITIS lies 3' northeast of the cluster. AURA/NSF MARTIN C. GERMANO

WWW.ASTRONOMY.COM 47 These computer-generated images from the Copernicus Complexio cosmological simulation show stellar halos of Milky Way-like galaxies. The visible streams result from tidally disrupted satellite galaxies. A.P. COOPER (NATIONAL TSING HUA UNIVERSITY, TAIWAN)/W. HELLWING AND THE VIRGO CONSORTIUM

This discovery image of a giant, low-surface-brightness, looplike around edge-on spiral NGC 4013 was obtained with a 20-inch amateur telescope. The marked redder color of the stream material compared to the outer parts of the disk suggests that this loop did not originate from the disk itself, but rather is the tidal stream of a dwarf galaxy being destroyed by its interaction with NGC 4013. R. JAY GABANY

48 ASTRONOMY STUDYING GALAXIES with amateur images Advances in our understanding of galaxy formation aren’t just coming from large, professional telescopes. BY DAVID MARTÍNEZ-DELGADO AND R. JAY GABANY

FROM THE TIME amateur astronomers first peered into his equipped with modest telescope until the middle instruments as well. One of the 19th century, profes- such amateur was sanitary sional telescopes required engineer Andrew Common. the observer to look In 1883, he took the first Fthrough an eyepiece. As a photograph of faint struc- result, astronomers manu- tures in the Orion Nebula ally logged mountains of (M42) that were not visible information and telescopic through an eyepiece. drawings in journals. Others, photographing a Then came photography. plethora of objects, quickly Almost from its inception, followed. photography offered the tantalizing prospect of serv- Paving the way ing as a tool to discover and As the 21st century document new, hitherto- dawned, the digital imag- unseen phenomena. In fact, ing technology that had by the beginning of the already replaced chemical 20th century, advancements photography at professional in photography enabled observatories began to career astronomers to lay trickle down into consumer down their pencils and products. This enabled trade their telescope amateur astronomers to eyepieces for glass plates purchase, at a reasonable coated with photographic cost, computer-controlled emulsions. charge-coupled device In addition to appealing (CCD) cameras expressly Dwarf galaxy Donatiello I was captured through a Takahashi FSQ-106 refractor to professional astronomers, designed for use with small at f/3.6 and a commercial CCD camera at the Avalon Merlino, the personal remote observatory of Avalon Instruments. The total exposure time was 24,300 seconds this potential captured the telescopes. At the same through a luminance filter. The zoomed-in panel shows a red-filtered image of imagination of resourceful time, motorized mounts Donatiello I from the 10.4-meter Gran Telescopio Canarias in La Palma, Spain. G. DONATIELLO

WWW.ASTRONOMY.COM 49 driven by electronic maps of the sky enabled amateurs to place any celestial object at the center of an electronic imaging chip and track it with high precision. As a result, modest equip- ment became a tool for obtaining ultra-deep images that could capture the outskirts of nearby massive galaxies and survey vast areas of the sky with unprecedented depth. This enabled a new type of collaboration between world-class amateur astroim- agers and international teams of professional astronomers exploring one of the funda- mental questions in modern astrophysics: How did massive galaxies like our Milky Way come to be? The standard model of the universe’s formation predicts that the elegant galactic spirals we see today, including our own Milky Way, arose hierar- chically. They did this by capturing much smaller gal- axies, some only composed of dark matter. State-of-the-art computer models indicate the and its neighbors should still contain evidence of this ancient galactic cannibalism. During the last decade, This wide-field mosaic of the amateur telescopes have Magellanic Clouds was taken through revealed, in many cases for the a Canon EF 50mm f/1.4 USM prime lens from La Silla Observatory, Chile. first time, an assortment of YURI BELETSKY large-scale tidal structures

The Small Magellanic Cloud around nearby massive galax- shows a lot of detail through a Canon ies. They also have imaged EF 200mm f/2.8L lens from Hacienda formerly unknown nearby Las Condes, Chile. A faint, shell-like structure composed of young stars is low-surface-brightness star visible on the northeast side (upper systems. And amateurs using left in this image) of the galaxy. YURI BELETSKY/FABIAN NEYER/BERNHARD HUBL telephoto lenses have traced interactions between the Magellanic Clouds and other Milky Way satellite galaxies. All of these amazing images have provided evidence to support our understanding of galactic evolution as predicted by current simulations.

50 ASTRONOMY • FEBRUARY 2021 Amateurs at work target using high-throughput variations from different Ultra-deep observations of luminance (clear) filters for sources. These artifacts com- nearby spiral galaxies and visible-light imaging. To plicate or mask the detection This discovery image of a stellar regions around them have capture fuzzy emission line of faint structures, and their stream in the halo of the nearby dwarf starburst galaxy NGC 4449, located been obtained by world-class structures in galactic halos, correction adds significant 12 million light-years away in the American, European, and imagers use narrowband observing time overhead to constellation , was detected with deep, integrated- Chilean amateur astroimag- Hydrogen-alpha filters. the data-gathering process. light images from a 20-inch amateur ers. They operate privately These observations demon- telescope. R. JAY GABANY owned observatories that strate in several ways the fea- use high-quality apochro- sibility of smaller telescopes to matic and -Chrétien detect very faint diffuse struc- telescopes with apertures tures in large around between 4 and 32 inches (0.1 nearby galaxies. First, small and 0.8 meter). Each observ- short-focal-length telescopes ing location features spectac- combined with single-chip ularly dark, clear skies with cameras cover a larger field typical seeing less than 1.5". of view. Second, the use of These modest telescopes single-chip detectors also — and, in some cases, makes it easier to flatten the telephoto lenses — are coupled external regions around with off-the-shelf CCD cam- galaxies in comparison to eras equipped with the latest standard multi-chip detector generation of imaging chips. arrays used with professional

THE STANDARD MODEL OF THE UNIVERSE’S FORMATION PREDICTS THAT THE ELEGANT GALACTIC SPIRALS WE SEE TODAY, INCLUDING OUR OWN MILKY WAY, AROSE HIERARCHICALLY.

They can probe vast sky areas with unprecedented depth — approximately three magni- tudes fainter than either classic photographic plate surveys like the Palomar Observatory Sky Survey or more recent digital surveys like the (SDSS). Camera sensitivity, fast operation, and lack of the competition for observing time typical of professional observatories places these low-cost robotic amateur facilities at the front line of ultra-deep imaging. They Stellar streams around M63 are allow high-impact research the remnants of a that was disrupted by the large of structures in nearby telescopes. Finally, observa- Searching for stellar spiral. Their presence was confirmed low-surface-brightness galax- tions with large telescopes are streams in this image, taken with a 20-inch ies. Doing so requires mul- sometimes subject to glare Computer simulations pre- amateur telescope located high in the Sacramento Mountains of tiple seven- and eight-hour from nearby bright stars and dict that the stellar halos of New Mexico. R. JAY GABANY exposures of each galactic significant sky background massive galaxies contain an

WWW.ASTRONOMY.COM 51 These clear luminance filter images of nearby galaxies from the Stellar Tidal Stream Survey show large, diffuse light structures in their outskirts. A color inset of the disk of each galaxy has been over-plotted for reference. D. MARTÍNEZ-DELGADO/ R.J. GABANY/K. CRAWFORD/K. TEUWEN/A. BLOCK/ J. SCHEDLER/M. HANSON

Located in the constellation Leo, extensive debris shells from the accretion of one or more long-gone satellite galaxies encompass spiral galaxy NGC 3521 like a bubble. Data for this image were collected through a 20-inch amateur telescope. R. JAY GABANY

many thousands of light-years into space, often on both sides of the host galaxy. We have also found iso- lated shells, giant clouds of debris floating within halos, jetlike spikes emerging from galactic disks, giant plumes, and large-scale diffuse struc- tures. All of these are possibly related to the remnants of ancient satellites that are now thoroughly disrupted. One important highlight of this survey was the discov- ery of a stellar stream around NGC 4449, an isolated irreg- ular galaxy similar to the Large Magellanic Cloud. This is the lowest-mass galaxy with a verified stellar stream. Such a discovery suggests satellite assortment of tidal debris requires long-exposure, faint structures is compelling accretion also can play a sig- streams that long exposures wide-field images encom- evidence that supports the nificant role in building up should reveal. The most spec- passing the outskirts of the hierarchical nature of galaxy stellar halos around low-mass tacular examples are those host galaxies. Working with formation predicted by the galaxies as well as possibly that wrap around the host amateur astroimagers over standard cosmological model. triggering starbursts. galaxy and roughly trace the the last decade, we have In addition to circular fea- orbit of the progenitor satellite imaged nearby spiral galaxies tures similar to the Sagittarius Discovering satellite galaxy that created them. as part of the Stellar Tidal stream surrounding the galaxies These streams cannot be Stream Survey. Milky Way, our data have Searching for stellar streams resolved into individual stars This observational effort revealed enormous structures with deep amateur images and thus appear as elongated, has discovered almost 50 resembling open umbrellas has also led to the discovery diffuse light features with previously undetected tidal with long, narrow shafts. of numerous faint dwarf sat- an angular extent of several streams around our targets. These terminate in a giant ellite galaxies around a hand- arcminutes. Detecting them The extraordinary variety of shell of debris extending ful of nearby spirals. This is

52 ASTRONOMY • FEBRUARY 2021 intriguing because sophisti- This image presents in outstanding detail an extended stellar cated computer simulations tidal stream wrapping around the predict a large number of edge-on spiral galaxy NGC 5907, located about 53 million light-years small dark matter halos in the away in the constellation Draco the local universe. But our theory Dragon. This picture shows how the of galaxy formation is still accretion of a low-mass satellite galaxy can produce an interwoven, unclear as to how many of rosettelike structure of debris these are in the form of lumi- dispersed in the halo of its host nous star systems. Therefore, galaxy. R. JAY GABANY astronomers want to conduct a full inventory of dwarf gal- low-cost telephoto lenses to axies, both those orbiting as obtain deep images of the satellites and isolated dwarfs Clouds. One panoramic view that are in the vicinity of revealed a never-before-seen, nearby massive galaxies. The dense, shell-like area of stars only way to detect them is by in the outskirts of the Small surveying vast regions with Magellanic Cloud. deep images. Research using photomet- Only a few organized astro- ric observations from the imaging groups are searching Survey of the Magellanic for low-surface-brightness Stellar History revealed the satellite galaxies. Some mem- shell is mainly composed of bers of the Stellar Tidal young stars. It suggests the Stream Survey are also structure resulted from a involved in the Dwarf Galaxy star-formation event, likely Survey with Amateur triggered by gravitational interaction with the Large ISOLATED DWARF SPHEROIDAL GALAXIES ARE MADE Magellanic Cloud and/or the EXCLUSIVELY OF OLD STARS WITH LITTLE GAS TO FUEL Milky Way about 150 million years ago. Recent studies STAR FORMATION. with the found the two Telescopes. Additionally, the astroimager Giuseppe the Milky Way’s two larg- Magellanic Clouds had a Tief Belichtete (Very Long Donatiello during a visual est galactic satellites, the head-on collision about Exposed) Galaxies project is inspection of a deep image Magellanic Clouds, through the same time. run by German and Austrian produced with a 5-inch mapping their outskirts. imagers. These groups look refractor. The discovery was These regions should still Can amateurs for dwarf galaxies in subsequently confirmed with contain clues about past inter- contribute? long-exposure images using SDSS images and follow-up actions between the Clouds Based on these results, it’s software that searches for observations by the 3.6-meter that left visible imprints such clear that advances in our likely candidates and then Galileo and the 10.4-meter as distortions, clumps, arcs, understanding of galaxy for- extracts their photometric Gran TeCan telescopes, both and dense stellar areas. mation needn’t be obtained and structural characteristics. located in the Canary Islands. With that purpose in only by large, professional Isolated dwarf spheroidal This low-surface-brightness mind, we performed a deep, instruments. Important sci- galaxies are made exclusively stellar system, located about wide-field imaging survey entific results that further of old stars with little gas to 1° from Mirach (Beta [β] of the periphery of the our understanding of how fuel star formation. These Andromedae), is suspected Magellanic Clouds. Inspired the universe formed can be distant star systems are of to be the most isolated dwarf by the photographic plate obtained when amateurs with huge interest because they galaxy in the Local Group. work of French astronomer modest telescopes collaborate act as laboratories where Gérard de Vaucouleurs in the with professionals with big astronomers can study why Magellanic Cloud ’50s, this modern project used objectives. they stopped forming stars interactions about 10 billion years ago. Another important approach David Martínez-Delgado is an astrophysicist at the Instituto de For example, Donatiello I to understanding the for- Astrofisica de Andalucia in Spain who detects galactic fossils around is a mation and evolution of nearby galaxies. R. Jay GaBany is an award-winning California discovered by Italian dwarf galaxies is studying astroimager.

WWW.ASTRONOMY.COM 53 We review Celestron’s 60th

WHEN I WAS A TEENAGER, new to observing the sky, I spent a year wan- dering across the Milky Way armed with nothing more than a pair of 7x50 binocu- lars. Then a miracle happened: I received a Celestron 8, 1976 vintage, as a birthday present. It changed my universe forever. From the cornfield behind our Ohio subdivision, the telescope opened up completely new vistas — star clusters, nebulae, and galaxies. Not only could I see hundreds of spectacular sky objects, but I was seeing things like the , which the old-fashioned literature of the time contended was beyond the reach of an 8-inch scope. Now I feel like I have undergone another telescope revolution. Last year Celestron celebrated its 60th anniversary. As part of their festivities, they produced a new 8-inch Schmidt-Cassegrain Telescope (SCT), one that rolls all of the company’s fanciest fea- tures into one package. With a built-in wide-field camera, it aligns itself in a matter of minutes, requiring

The telescope’s carbon-fiber tube is both lightweight and very strong, giving this model a high-tech appearance.

Celestron’s most sophisticated 8-inch SCT ever features a revolutionary system that aligns itself so that users can simply punch in object names and designations on a keypad and slew to thousands of targets. The NexStar Evolution 8HD With StarSense, a limited-edition telescope, combines all of Celestron’s fanciest trappings to produce a superb, top-of-the-line ainsntrumennt. BY DAiVIvD J. EICeHER //r IMAGsES BYa CELESrTRONy C8

minimal knowledge on the part of the Out under the stars user. It then slews to any of 40,000 targets PRODUCT INFORMATION The first thing you need to do with this within its onboard computer’s database. scope is set it up on level ground and run Its multicoated optics are of the highest Celestron Limited-Edition a program that enables the StarSense unit caliber, and the three included eyepieces NexStar Evolution 8HD Telescope to calibrate itself. Included instructions are sensational. This is the ultimate With StarSense, and a to an online video tutorial 8-inch SCT of its time, and I was happy 60th Anniversary Edition make that very simple. That first night to be able to put it through its paces over Type: Schmidt-Cassegrain reflector I was in a hurry, so I set it up on my the past few weeks. Aperture: 8 inches (203 mm) driveway to give it a quick run-through. Focal length: 2,032 mm Although a portion of the sky was Setup and inspection Focal ratio: f/10 blocked by a tree and the house, I was Assembly was relatively straightforward, Optical tube length: 17 inches (43.2 cm) curious to see what would happen. and a helpful booklet walks owners Weight: 42 pounds (19 kg) fully So began my adventure with StarSense through the process. I went slowly, read assembled Autoalign. The camera mounts atop the everything carefully, and within an hour Price: $2,599 scope’s tube with a heavy bracket and had everything set up in my living room Contact: Celestron plugs into a port on the mount. To begin for inspection, charging of the onboard 2835 Columbia St. the calibration procedure, you start with battery, and preparation for a night of Torrance, CA 90503 the scope’s tube positioned horizontally. observing. 310.328.9560 A hand controller allows you to input With the telescope assembled, I www.celestron.com choices and, once the scope is aligned, couldn’t help but be struck by its quality target countless objects. I uncorked the and elegance. It features a scope’s mirror, the StarSense cam- carbon-fiber tube; multicoated, era’s cover, and the diagonal’s high-transmission optics (what cover before plopping a very nice Celestron calls “Edge HD”); a E-lux 32mm Celestron eyepiece sturdy single-arm mount; and, of into the diagonal. course, the alt-azimuth mounting I powered the scope on, chose enabled by the computer control of “Align” on the hand controller, set the scope. The company seemingly the time, date, and time zone, spared no details: The machining then stepped back and watched. is top-notch and the hardware is Over the course of about solid, a 2" focuser and star diago- 10 minutes, the scope slewed to nal came along with the package, and fro and occasionally noted on and the tripod is heavy duty. The the controller that it had imaged a onboard battery holds a charge for certain number of stars. Would Celestron supplies an array of accessories with more than 10 hours at a time. The this scope, allowing users to enjoy a luxurious this work with the handicap I gave it in included eyepieces are very nice, with a telescopic experience. my rush to test the scope? After a short 2" 32mm “porthole” for deep-sky observ- time, “Alignment complete” came up on ing and higher-power 1¼" eyepieces of objects manually for years. Would this the controller. 15mm and 9mm focal lengths. computer-controlled system with its Next, I followed the protocol by cali- The StarSense system was really what database of tens of thousands of objects brating on a known star. I punched in intrigued me. I am an old-school, — which it would apparently use to align “Vega” and the scope immediately slewed star-hopping guy who has taken great itself before hopping between galaxies upward, capturing Vega’s position. When pride in learning the sky and finding — win me over? I peered into the eyepiece — low power,

WWW.ASTRONOMY.COM 55 no doubt — the star was dead center. The makes one spoiled quickly. There was final step is a calibration on the star itself the Trifid, glowing faintly; the unmis- (Vega in my case), and this can be done takably bright popped with a high-power eyepiece to maximize fiercely, and the delicate light of the precision. You can then realign the Eagle Nebula appeared well defined. StarSense and, in another few minutes, The computer-controlled database the mount is ready to use all night; you makes punching in some of the can simply punch in targets and let the lesser-known objects like clusters M23, scope slew to them. M25, and NGC 6603 easy. I worked my This full calibration procedure needs way up to M11, which was incredible, to be performed only once, when the and then viewed some globulars — M22 StarSense Autoalign is first attached to the in particular was a killer, looking quite telescope’s tube. From there, a full calibra- photographic. tion is not needed unless the StarSense is I turned toward some favorite plan- bumped or the bracket removed. etary nebulae I hadn’t viewed in a while. Wow. Here is the kind of telescope The , high in the sky, that could revolutionize astronomy. This knocked my socks off — it looked like a is a telescope that anyone can use without glowing photo in a rich starfield of col- any knowledge of old-style polar align- Celestron’s StarSense system uses a remarkable orful . What incredible beauty. But wide-field camera to image star patterns around the ment. It is really quite amazing to see this sky, allowing the telescope to understand where it is Cygnus and Aquila had many other work just as magically as is advertised, and how it’s aligned before automatically slewing to treasures, and I viewed NGC 6781, with objects showing up dead-centered, a target. NGC 6894, NGC 7008, and NGC 6826 just as requested from the database. (just to name a few). They all appeared quite well defined, with the blue-green Computer-controlled colors showing well, and were visible at heavens low powers, growing more spectacular as I gave this telescope a more thorough I increased magnification. test run from my backyard in Wisconsin, I then took a shot at some widely scat- where I can see the Milky Way and a tered objects just to see the range of good smattering of faint stars. The tele- views the telescope could provide. The scope performed most impressively. I Andromeda Galaxy appeared bright and can’t wait to get it underneath a really oval, with well-defined dust lanes close prime sky like that of southern Arizona. to the nucleus. The Owl Cluster in I commenced my journey with Jupiter Cassiopeia, with its bright deep yellow and Saturn, each looking really fine, with chief sun, was an old friend I revisited. nice cloud details, even at low power. All Double stars like Mizar and Albireo were the moons that should have been present simply stunning, set in black starfields, were, and the higher-power eyepieces and galaxies like M81 and M82 floated provided a splendid view early on, even majestically in space. though the seeing had not fully settled As the night went on, I found this down for the evening. The scope’s standard visual back employs a telescope to deliver on everything I had 2" star diagonal and can accommodate both 2" But I was eager to tour deep-sky objects and 11/4" eyepieces. hoped for: The optics are sharp, the and so I plopped the 32mm eyepiece back accessories luxurious, the tripod over- in and went to work. Everything I looked The did not disap- built and very stable, the craftsmanship at showcased the quality of the telescope’s point, with its gauzy areas of bright of the optical tube and the electronics optics — the views were crisp and well gray-green nebulosity and the sparkly, first-rate. I have a soft spot for the old defined, and I saw all the details in clus- well-populated NGC 6530. 1976 Celestron 8, with which I made my ters, nebulae, and galaxies that I would For a time, I walked up the line of bright initial thousands of observations, and expect to see from a suburban site. The clusters and nebulae in Sagittarius and which is now in my basement. But 32mm eyepiece provides a sharp, flat field, Serpens. Only needing to input the there’s a new Celestron in town, and this yielding crisp stars all across the view. numbers of Messier and NGC objects magnificent model is going to be hard for any such portable instrument to overcome. This is a telescope for a new At press time, Celestron had announced that they have sold out of this exclusive anniversary age of . model. However, almost exactly the same telescope — without the carbon-fiber tube and a few bells and whistles — is available. The Celestron NexStar Evolution 8HD With StarSense functions in exactly the same way as the anniversary edition. You can find out more about it here: David J. Eicher is editor of Astronomy www.celestron.com/products/nexstar-evolution-8-hd-telescope-with-starsense. and has been using telescopes for more than 40 years.

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WWW.ASTRONOMY.COM 57 SECRET SKY

LEFT: On June 10, 2020, an with only a partial penum- Earth-sized sunspot, AR bra that doesn’t completely 2765, from brewing solar cycle 25 could be seen surround the core; and fully A sunspot bino through handheld 8x42 dressed sunspots, which are binoculars. RIGHT: Two Earth-sized and feature a days later, when the spot’s umbra was smaller dark core, an umbra, and a challenge and less apparent, it was penumbra. difficult to see, even when the author braced the I began systematically Search for small spots with both eyes. binoculars. North is up observing the Sun on and east to the left. SDO/HMI June 10, 2020. That day, I used handheld 8x42 binocu- lars to see without difficulty a fully dressed Earth-sized sunspot labeled AR 2765. (AR stands for active region.) The evolved spot was in the Sun’s southern hemisphere and had already sailed past the central meridian. Two days later, the fore- shortened spot appeared both For safe binocular smaller and less apparent, solar viewing, you can make a simple device The long-awaited next solar cycle is showing making it more difficult to detect. Only when I braced using certified signs of awakening, and so is the time for the binoculars against a wooden post could I resolve the eclipse-viewing observers to search for naked-eye sunspots. spot, which looked more smoky gray than black. glasses, scissors, and glue or tape. Cut and But at the beginning of a new cycle, the first spots to A similar situation occurred July 25, when another fit the glasses into a appear are generally too small to be detected without Earth-sized sunspot (AR 2767) appeared in the Sun’s cardboard box large optical aid. Using safe solar filters in front of binoculars southern hemisphere. As for AR 2765, handheld 8x42 enough to fit over the front of your will help bring some of these devilishly delightful spots binoculars easily brought it into view. It remained vis- binoculars. Make sure into view. Unfortunately, the task is not easy. ible until July 31, when the spot’s highly foreshortened the fit is secure and umbra diminished in apparent size enough that it that there are no light leaks. STEPHEN JAMES Cycle 25 brewing? became a challenge to see through the binoculars. It O’MEARA In their February 2020 article in Research Notes of the vanished from view the next day. American Astronomical Society, Dibyendu Nandy from By August 5, a more challenging spot (AR 2770) in the Center of Excellence in Space Sciences India and his the Sun’s northern hemisphere had slid into binocular colleagues argue that solar cycle 25 may be dawning. view. That day, the foreshortened spot was difficult to No one knows exactly how a new solar cycle starts, but see even with braced 10x50 binoculars. I had to know it’s thought to be based in a complex interaction of ion- exactly where to look to pick it out. Sighting AR 2770 ized gas and the Sun’s magnetic field. We do know that was similar to spotting Venus in the daytime — if you spots in a new cycle will have their magnetic poles look away for an instant, it’s gone. reversed from those in the last cycle — in this case, cycle Two days later, however, the Earth-sized spot was a 24, which ended around December 2019. cinch through handheld binoculars. I finally lost sight Since November 2019, solar astronomers have been of it on August 11, the day after an enigmatic light observing new sunspots with reversed polarity around bridge had split the spot in two, and before it had 25˚ north and south latitudes. And this happens to be dwindled into a naked pore. exactly where they expected new spots from solar cycle 25 to appear. Seeing such spots is a positive sign that a Observe in sunlight new solar cycle is in the making. By the time you read this, other Earth-sized spots may be moving across the Sun. Each offers you a chance to The binocular challenge test your direct vision through filtered binoculars. I Before we get into viewing cycle 25 sunspots, two defi- want to learn how small of a sunspot you can see, espe- BY STEPHEN nitions. A sunspot’s umbra is the dark inner part. Its cially if you use tripod-mounted binoculars or those JAMES O’MEARA penumbra is the lighter outer region. Currently, the larger than 10x50. Good luck, and, as always, send what Stephen is a globe- stammering start of cycle 25 has been creating three you see and don’t see to [email protected]. trotting observer who is always looking types of spots: Short-lived naked cores, which are state- for the next great sized dark spots without any penumbra; partially BROWSE THE “SECRET SKY” ARCHIVE AT celestial event. dressed proto-sunspots, which are Moon-sized marks www.Astronomy.com/OMeara

58 ASTRONOMY • FEBRUARY 2021 BINOCULAR UNIVERSE

is an F-type supergiant 1,300 light-years away. It makes Bound across the perfect jumping-off point to find an object in celestial limbo. Glance 1.5° due east of Arneb. Can you make out a the sky misty knot of four faint stars? That’s NGC 2017. Originally classified as an open cluster, we now know Lepus the Hare offers some less-explored celestial sights. that NGC 2017 is an that happens to also include the multiple-star system h3780. With most At this time of binoculars, we can see that the system’s brightest star, year, all eyes are at 6th magnitude, is framed by a tight triad of on Orion, Taurus, 8th-magnitude attendants. Canis Major, Gemini, and Lepus contains a single entry in ’s Auriga, with their bevy of famous catalog: M79, an out-of-the-way globular clus- stellar and deep-sky trea- ter. To find it, bunny-hop 3° from Arneb southwestward sures. But that leaves other to (also known by the proper name Nihal), constellations to pass by and then repeat the leap, continuing in the same direc- unnoticed and underap- tion. Most globular clusters around the center preciated. This month and of our galaxy, placing them in our summer sky. But a next, let’s explore the rest of few, like M79, lie in the opposite direction. M79 sits the winter sky. 60,000 light-years from the galactic center, about 10,000 South of Orion’s knees, light-years farther than our solar system. Some believe marked by Rigel (Beta [β] that this points to an extragalactic origin — that M79 Through binoculars, Orionis) and (Kappa was once affiliated with a tidally disrupted dwarf galaxy M79 (NGC 1904), a [κ] Orionis), are a half-dozen or so fainter stars that known as the Canis Major Dwarf. collection of 100,000 stars, appears as a form the constellation Lepus the Hare. Through binoculars, M79 appears much like Messier single, fuzzy star. Even though its brightest star shines no better than himself described it in December 1780, two months ADAM BLOCK/NOAO/AURA/NSF magnitude 2.6, Lepus is apparent in suburban backyards after his contemporary, Pierre Méchain, discovered it: if there is a good view to the south. Directly below the “Nebula without a star; the center bright; the nebulosity imaginary line connecting Rigel and Saiph lie four of a little diffuse.” In reality, of course, M79 is a spherical the Hare’s brightest stars, set in a distinctive trapezoid. collection of about 100,000 stars. You will find this Beginning at the northernmost of the four and moving fuzzy little patch of light just northeast of a clockwise, there’s Alpha (α), Beta (β), Gamma 5.5-magnitude star, SAO 170351. (γ), and Delta (δ) Leporis. All fit comfortably Lastly, we come to a challenging treasure, into a 7° field of view through binoculars. the tiny but colorful planetary nebula IC 418, Of the four, Gamma will immediately This month better known as the Spirograph Nebula catch your eye. That’s because it has a friend, and next, (thanks to a famous image from the Hubble a 6th-magnitude star 97" to its north. The let’s explore Space Telescope). I received a note last winter 4th-magnitude star you see by eye alone is from reader Scott Harrington (no relation) known as Gamma A, while its fainter com- the rest reminding me just how bright this planetary panion is Gamma B. The Gamma system lies of the nebula is, and yet how few of us have ever 29 light-years away, with the stars separated winter sky. seen it. Although many sources list it as from each other by an estimated 870 astro- photographic magnitude 10.7, it appears nomical units — where 1 , much brighter by eye, bringing it well within or AU, is the average distance between Earth the limits of most binoculars. IC 418 is some- and the Sun. Together, they create one of the most strik- times called the Raspberry Nebula, for its prominent ing binocular binaries in the entire sky. Each is bright pinkish color through giant backyard telescopes. With enough and separated far enough from the other that most binoculars, however, it appears grayish, with pos- any binocular can resolve them. When I study them sibly a blue or green tinge. Try it for yourself and let me closely, Gamma A impresses me as yellow-white, know what you see. although some report it as greenish. Gamma B is a Questions, comments, suggestions? Contact me BY PHIL subtle orange. Defocusing your binoculars slightly will through my website, philharrington.net. Until next HARRINGTON Phil is a longtime help enhance the delicate colors. month, remember that two eyes are better than one. contributor to Next, shift your attention diagonally across the , Astronomy and the Lepus trapezoid to also known by the BROWSE THE “BINOCULAR UNIVERSE” ARCHIVE AT author of many books. proper name Arneb. The Hare’s brightest star, Arneb www.Astronomy.com/Harrington

WWW.ASTRONOMY.COM 59 [δ] Orionis), the most westerly of Orion’s Belt stars. This OBSERVING BASICS 2nd-magnitude is accompanied by a much fainter partner (magnitude 6.8, to be exact). Fortunately, the lesser star is 56" away. Both were well seen at 70x. A degree southwest of (Zeta [ζ] Orionis), the easternmost Belt star, is the multiple star Sigma (σ) Observe Orion Orionis. In the 60mm refractor at 117x, Sigma was a triple: the 4th magnitude primary accompanied by two 6th-magnitude stars on one side separated from the main with ease star by 13" and 42". I then pointed my scope north to Lambda (λ) Orionis, brightest of the triangle of stars that Even a small scope reveals this timeless winter treat. forms Orion’s head. This eye-pleasing duo (magnitudes 3.5 and 5.5, separation 4.3") was split with 117x. A year ago, I Turning to deep-sky objects, I made my way north- N received an east towards Xi (ξ) and Nu (ν) Orionis, and the nearby j i email from open cluster NGC 2169, sometimes called the 37 Cluster. NGC 2169 ORION Joe McCoubrey, a NGC 2169 is comprised of two stellar groups — each 13-year-old astronomy forming one of the numbers. Just 7' in apparent diam- 1 enthusiast from eter and comprised of a little more than a dozen stars, h / Bennett, Colorado, the 37 Cluster was best seen at 117x. Unfortunately, my / 2 who asked me for a list scope was equipped with a standard star diagonal, _ / 3 Betelgeuse a of the best winter sky which produced a mirror image of the 37. / 4 targets for small tele- From NGC 2169, I moved past Betelgeuse and trav- t scopes. The request eled an equal distance beyond to the reflection nebula, / 5 reminded me that I M78. Similar in size to NGC 2169 and just 8th magni- E / 6 hadn’t made a small- tude, it required a patient, minutes-long search with low M78 scope into the magnification (23x) before a rather faint puffball b winter skies for years. appeared in the field. I tried higher magnifications, but Alnitak c ¡ m To remedy this over- 70x seemed to offer the best view. NGC 1981 sight, I decided to take I completed my journey at Orion’s Sword and the e¹ f M43 out my small scope constellation’s pièce de résistance: the Orion Nebula M42 o (a 60mm refractor) and (M42/43). A magnification of 23x brought the entire ` 5° explore a classic winter Sword into view, from the loose open star cluster NGC g Rigel constellation: Orion. 1981 near the north end down to Iota (ι) Orionis and the I began with Rigel. wide Struve 747 near the south. Since Iota is Orion holds a plethora This 0.1 magnitude double and too close for a low-power split (the magni- of beautiful celestial sights you can explore, blue giant was a dazzling sight in the little scope. That’s tude 7.7 companion is 12.5" from the magnitude 2.8 and many of them are especially true at a magnification of 117x, where it flick- main star), I quickly switched to 117x for a clean split. accessible using a ered like a diamond under somewhat turbulent skies. I The Orion Nebula was a magnificent sight in the little small telescope. ASTRONOMY: ROEN KELLY used this high magnification (around the refractor, especially at 70x — a magnifica- upper limit for a 60mm scope) in a vain tion that captured the expanse of the nebula attempt to see Rigel’s 7th-magnitude If Rigel was while still resolving the four brightest mem- companion, located about 10" away. a diamond, bers of its embedded multiple star Theta1 Theoretically, a 60mm refractor should be Betelgeuse (θ¹), the Trapezium. It would take an entire able to split double stars as close as 1.9", but column to do justice to this region, as it’s one that’s only if the component stars are rela- was sparkling of the finest deep-sky targets in the entire tively bright and similar in magnitude. like a yellow- sky. (In fact, I did that in my February 2019 Rigel’s companion is 400 times fainter, so orange topaz. column, “Experience the Orion Nebula.”) it’s easily lost in the bright star’s glare. I And although everything described in chose to save Rigel and its partner for a night this article can be viewed through large- with a steadier atmosphere. aperture instruments, there’s a sense of accomplishment Next up was the red supergiant Betelgeuse. The color that comes with snagging a good look through a modest contrast between ruddy Betelgeuse and blue-white Rigel instrument like a 60mm refractor. So, if you own one, was striking. If Rigel was a diamond, Betelgeuse was take it out for a night under the Orion sky. BY GLENN CHAPLE sparkling like a yellow-orange topaz. Betelgeuse wasn’t Questions, comments, or suggestions? Email me at Glenn has been an alone, either. Just 20' to its south stood the pretty double [email protected]. Next month: more observer’s avid observer since a friend showed star Struve 817 (magnitudes 8.7 and 8.9, separation lists. Clear skies! him Saturn through 18.6"). This delicate little duo humbly shining next to a small backyard brash Betelgeuse was a captivating sight! BROWSE THE “OBSERVING BASICS” ARCHIVE scope in 1963. Looking for more doubles, I moved to Mintaka (Delta AT www.Astronomy.com/Chaple

60 ASTRONOMY • FEBRUARY 2021 NEW PRODUCTS

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WWW.ASTRONOMY.COM 61 ASK ASTRO Astronomy’s experts from around the globe answer your cosmic questions.

Spiral arms show the same structure whether composed of billion-year-old stars or million-year-old stars. This indicates that the arms are the result of a persistent pattern of stars rather than particular stars causing the structures. That pattern is caused by a density (pressure) wave that spirals from the edge of the disk to the center and back out again, creating the visible spiral arms of the galaxy. Essentially, as stars and gas move through the pattern, they bunch up in the wave crests, like a stellar traffic jam, and then eventually break past the crest and continue on their orbit. Both planetary rings and protoplan- etary disks can have density waves and spiral structure. Planetary rings are made of small amounts of debris Some 520 light-years away lies AB Aurigae, trapped in a particular orbit. Sometimes which has a twisted they are perturbed by moons that cause waves. planetary disk. The According to computer simulations, observed spirals spirals around AB Galactic Aurigae are likely in protostellar disks are from density waves driven by caused by baby planets forming in the disk. planets coalescing in Debra Elmegreen the dust surrounding traffic jam Professor of Astronomy on the Maria Mitchell Chair, Vassar College, the young star. ESO/ Poughkeepsie, New York BOCCALETTI ET AL. I WHAT CAUSES THE FORMATION SINCE ’ FLYBY OF Q OF SPIRAL ARMS IN GALAXIES? QI ARROKOTH IN JANUARY 2019, IS DO SPIRAL ARMS FORM IN OTHER THE SPACECRAFT ZOOMING TOWARD A FLATTENED GROUPS OF ORBITING NEW TARGET? IS NEW HORIZONS ABLE OBJECTS, LIKE PLANETARY RINGS AND TO SEARCH FOR ? PROTOSTELLAR DISKS? Douglas Kaupa Robert Harrison Council Bluffs, Iowa Albuquerque, New Mexico New Horizons is healthy and routinely study- Spiral arms in galaxies can form by a combina- AI ing the Belt environment and Kuiper AI tion of processes. In a spiral galaxy, everything Belt objects (KBOs) it passes in the distance. For the orbits at the same speed, meaning stars and gas near next year or so, the New Horizons team is using the the center of the galaxy complete an orbit in less time largest telescopes on Earth — such as the Subaru than objects farther out. This effect is referred to as telescope in Hawaii — to find more KBO targets. From differential rotation. So, in the time it takes an inner there, we can determine if New Horizons has the fuel star to complete one revolution around its galaxy, an to perform a flyby. outer star might have only finished half a revolution. We should know the results of our first search by fall Differential rotation naturally generates spirals as the or early winter 2020, and we will observe again using galaxy rotates. Galaxies like the Milky Way have rotated ground-based telescopes between April and September a few dozen times — it typically takes 200 million years 2021. If either search succeeds in finding a potential for the entire galaxy to complete a revolution. If target, we would seek NASA’s permission to burn our differential rotation were the only process involved in engines to conduct another flyby. generating spirals, we would expect to see many tightly I personally consider Pluto to be the solar system’s wrapped spiral arms, like a wound coil. But most spiral ninth planet to honor its discoverer Clyde galaxies have only two to four main arms. and his contributions to . So, I call

62 ASTRONOMY • FEBRUARY 2021 from the center of the galaxy, suggesting it was kicked WHERE NEW HORIZONS IS NOW out of the galactic center. SEND US YOUR As to what happens to the rest of 3C186, the short QUESTIONS answer is that the galaxy will remain as it is. A galaxy Send your is held together by the collective mass of its stars, gas, astronomy questions and dark matter, and any gravitational effects of the Uranus Neptune via email to askastro@ central SMBH are negligible with respect to that of the astronomy.com, or whole galaxy. For example, the SMBH at the center of write to Ask Astro, P.O. Jupiter our own Milky Way — Sagittarius A* (Sgr A*) — has a Box 1612, Waukesha, Saturn Pluto mass only one-millionth the total mass of the galaxy. WI 53187. Be sure to tell us your So, Sgr A* only dominates the motions of the stars and Arrokoth full name and where gas in a very small central volume and not of the galaxy you live. Unfortunately, as a whole. we cannot answer all When two galaxies merge, their SMBHs will eventually questions submitted. coalesce into a new SMBH. In the case of 3C186, this new K U I P E R B E LT black hole likely received a “kick” from the gravitational New Horizons waves emitted during the SMBH merger, acquiring velocities up to several thousand miles per second. New Horizons is currently deep within the , about As a result of this kick, 3C186’s SMBH’s orbit began 48 astronomical units (AU) from the Sun, where 1 AU is the average Earth-Sun distance. After passing Arrokoth, New to oscillate around the galaxy’s core. Nearby stars and Horizons is on the hunt for a new Kuiper Belt object to fly by. gas were pulled along with it, in principle creating ASTRONOMY: ROEN KELLY observable effects such as distortions in the morphology and dynamics of the galaxy. However, since the SMBH’s Pluto planet nine. With regard to the hypothetical sphere of inf luence is very limited, the entire galaxy will object Konstantin Batygin and Michael E. Brown not suffer major disruptions, even if the black hole is believe causes the perturbations of KBOs’ orbits, the completely ejected. jury is still out on whether it is real. Scientists have But this does not mean that the overall influence of The galaxy 3C186 — looked for such a planet for many years and have not the central SMBH on the host galaxy is negligible! There itself the likely result been able to find it. are a number of extremely close relations between the of a previous galaxy merger — hosted the While it would be fun to look for new planets with mass of the SMBH and the properties of its host galaxy, merger of two super- New Horizons, large telescopes on Earth do a much known as scaling relations. These mean the host galaxy massive black holes. better job than the smaller telescopes New Horizons is and its SMBH essentially grow together. But, as we have The resulting gravita- tional waves are equipped with. New Horizons also has no internal seen, this cannot be due to the gravitational influence believed to have reaction wheels and relies on its thrusters to orient of the SMBH. There must be something else causing “kicked out” the newly itself, so slewing the spacecraft around to search for this relationship. created supermassive Stefano Bianchi black hole from the planets would waste precious fuel we could use for center of the galaxy. Associate Professor, Università degli Studi Roma Tre, Rome, Italy another flyby farther out in the Kuiper Belt. NASA, ESA, AND M. CHIABERGE S. Alan Stern (STSCI/ESA) Principal Investigator for New Horizons, Southwest Research Institute, Boulder, Colorado

WHAT WILL HAPPEN TO THE QI STARS IN THE GALAXY 3C186, NOW THAT THE CENTRAL SUPERMASSIVE BLACK HOLE HAS BEEN EJECTED FROM THE GALACTIC CENTER? WILL THEY SLOWLY DRIFT APART, OR WILL THEIR COLLECTIVE MASS HOLD THEM TOGETHER FOR A WHILE? Dennis Moore Houston, Texas

Located 8 billion light-years away, the galaxy AI 3C186 is home to an extremely bright galactic nucleus — the signature of an active supermassive black hole (SMBH). But this SMBH is about 35,000 light-years

WWW.ASTRONOMY.COM 63 READER GALLERY Cosmic portraits

1. HAWTHORNE’S A The Scarlet Letter (Sharpless 2–96) is an emission nebula in the constellation Cygnus the Swan. Astronomers suspect that it is part of supernova remnant SNR 65.2+05.7. • Jerry Yesavage

2. AWAY IT GOES An is the temporary disappearance of a celestial body due to the passage of another in front of it, from a certain point of view. The Moon occulted Mars on August 9, 2020. • Ricardo José Vas Tolentino

3. BLUE BEAUTY Abell 72 is a planetary nebula in the constellation Delphinus the Dolphin. This glowing shell of gas expanding outward from a dying Sun-like star spans 2 light-years. This image combines 18.6 hours of exposures. • Douglas J. Struble 1

2 3

64 ASTRONOMY • FEBRUARY 2021 4. FULL CIRCLE This 360° panorama shows the entire sky above Black Canyon of the Gunnison National Park in Colorado. The two-row composite has one row for the sky and one for the landscape, which was shot without tracking before it was completely dark, in order to retain detail. The image includes the Milky Way and lots of colorful airglow. • Vince Farnsworth

5. WAGGING ITS TAIL The tail of Comet C/2019 U6 (Lemmon) appears to touch open cluster M41 in Canis Major on May 27, 2020, from Tivoli — Southern Sky Guest Farm in Namibia. At the time, the comet stood a mere 20° above the horizon. • Gerald Rhemann

6. SOUTHERN BRILLIANCE The Southern Pleiades goes by several other names, including Caldwell 102, IC 2602, Collinder 229, and the Theta Carinae 4 Cluster. But its resemblance to the Pleiades (M45) makes “the Southern Pleiades” the name that resonates most with observers. Because it glows at magnitude 1.9, this cluster is easy to spot without optics. • Nicholas Clarke

7. FLASH FORWARD The green flash happens when long-wavelength light (red, orange, yellow) from the setting Sun is bent away from our eyes. These three exposures were captured a few seconds apart March 29, 2020, from Siesta Key, Florida. • Tom Fazekas

SEND YOUR IMAGES TO: 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 5 6 readergallery@ astronomy.com.

7

WWW.ASTRONOMY.COM 65 BREAKTHROUGH

HEAVY METAL STAR ATTRACTION Globular cluster NGC 6441 doesn’t get a lot of respect from amateur astronomers. Maybe its location in southern , which keeps it low in the sky from midnorthern latitudes, tips the scales against it. And its great distance of roughly 40,000 light-years doesn’t help. Yet NGC 6441 stands out among the Milky Way’s approximately 150 globular clusters. It ranks among our galaxy’s most massive and most luminous globulars, weighing some 1.6 million solar masses and shining with the light of 600,000 Suns. It also contains more metals — astro-speak for elements heavier than — than most globulars. Perhaps this stunning Hubble Space Telescope portrait will help NGC 6441 gain the respect it deserves. ESA/HUBBLE AND NASA/G. PIOTTO

66 ASTRONOMY • FEBRUARY 2021

B&H Photo – 800.947.9970 – bhphotovideo.com Astronomics – 800.422.7876 – astronomics.com Adorama – 800.223.2500 – adorama.com High Point Scientifi c – 800.266.9590 – highpointscientifi c.com OPT Telescopes – 800.483.6287 – optcorp.com Focus Camera – 800.221.0828 – focuscamera.com Optics Planet – 800.504.5897 – opticsplanet.com Woodland Hills – 888.427.8766 – telescopes.net Agena AstroProducts – 562.215.4473 – agenaastro.com SOUTHERN SKY BY MARTIN GEORGE April 2021 Mars hangs on at dusk

With autumn now in earlier by month’s end. The seeing, finer details pop into between the main stars in full swing, skygazers ringed planet shines at magni- view. Also keep an eye out for Alpha Cen is now near a mini- have their first opportunity tude 0.6 among the stars of the planet’s four bright moons mum, so that pair looks less of the year for early evening north-central Capricornus the — Io, Europa, Ganymede, and spectacular than usual. observing. For solar system Sea Goat. Callisto — which appear obvi- ’s two main compo- enthusiasts, however, only one For the best views of Saturn ous through any scope. nents shine at magnitudes 1.3 naked-eye planet graces the through a telescope, wait until Mercury remains promi- and 1.8 and stand some 4" evening sky. You can find it climbs high in the sky an nent during morning twilight apart. That is plenty wide Mars low in the northwest hour or two before twilight in early April. It rises about enough for any telescope to after darkness falls. The Red begins. You won’t be disap- 80 minutes before the Sun on split them. The view through Planet lies against the back- pointed. On April 15, the plan- the 1st, when it glows at magni- a high-quality refractor is drop of Taurus in early April, et’s disk measures 16" across tude –0.5 and is the brightest particularly impressive. The to the right and a bit below the while the spectacular ring sys- object between Jupiter and the brighter component is also a Bull’s luminary, Aldebaran. tem spans 37" and tilts 17° to eastern horizon. It disappears spectroscopic binary, meaning The red giant star, which our line of sight. Any scope in the Sun’s glare during April’s that the two suns lie so close to shines at magnitude 1.0, also shows the 8th-magnitude second week on its way to supe- each other that they can’t be appears slightly brighter than moon Titan, which circles rior conjunction on the 19th. split at the eyepiece, but a spec- the magnitude 1.3 planet. Saturn once every 16 days. Although Venus typically trum reveals their mutual Mars heads eastward rela- A 10-centimeter instrument appears brighter than any other orbital motions. tive to the background stars gathers enough extra light to point of light in the sky, it A fourth component of the this month, crossing the invis- reveal three or four additional remains out of sight this month multistar system shows up eas- ible border between Taurus and satellites. as it tracks across the sky with ily through binoculars. Look Gemini on April 24. Three About an hour after Saturn the Sun. It will return to view for a 5th-magnitude star posi- nights later, on the 27th, the rises, Jupiter pokes above the after sunset in May. tioned about 90" south of the planet passes just north of the eastern horizon. You won’t mis- main pair. 5th-magnitude open star clus- take the Sun’s largest planet for The starry sky James Dunlop of the ter M35. Plan to view this con- any other object — at magni- Once darkness falls during Observatory in junction through binoculars or tude –2.1, it shines brighter April, the Cross appears first cata- a telescope, but don’t expect to than any other planet or star prominent about halfway from loged Acrux as a double star in see any detail on the planet’s visible this month. Jupiter the southeastern horizon to the the 1820s. He wasn’t the first to 5"-diameter disk. spends most of April in zenith. The unmistakable con- notice its duplicity, however. A waxing crescent Moon Capricornus, but it pushes stellation is tipped on its side, Jean de Fontenay and Guy passes in front of Mars on across the border into Aquarius with the base of the Cross — Tachard observed the star from April 17. The best views in the the Water-bearer during the Acrux (Alpha [α] Crucis) — the Cape of Good Hope in 1685 Southern Hemisphere come month’s final week. farthest to the right. Acrux also while they were making their from Indonesia. In Jakarta, for As with Saturn, you’ll want ranks as the constellation’s way to the Far East. In his example, the planet disappears to wait until dawn approaches brightest star. account of the trip, Tachard behind the Moon’s dark limb before targeting Jupiter through But for those who prefer to described viewing Acrux at 13h32m UT and reappears your telescope. That’s because explore the night sky through a through the telescope: “Two from behind the bright limb higher altitudes deliver sharper telescope, Acrux stands out bright stars distant from one at 14h29m UT. views of the giant planet and its most because it is a fine double another about their own diam- You’ll have to wait until dynamic atmosphere. Jupiter star. In fact, for the past several eter only.” Tachard also after midnight to see another shows an alternating series of years, it has rivaled its better- recorded the third, distant planet. Saturn rises shortly bright zones and darker belts known cousin Alpha Centauri component. How do your after 2 a.m. local time in early on a disk that spans 36" in mid- in neighboring . observations compare when April and nearly two hours April. During moments of good That’s because the separation pointing a telescope at Acrux?

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B H _ YDR e A t STAR e P l _ r g oc e y MAGNITUDES u o s ` n e C T A Sirius A M N I I U N S 5 R O _ 6 0.0 3.0 U a R M S lus 1.0 4.0 c Regu EO M L 1 a 2.0 5.0 M4 M 4 a rs M 35 G ` E P C M ollu AN STAR COLORS IN x CE M I _ R N 3 A star’s color depends 7 W C as on its surface temperature. tor R NO The hottest stars shine blue MI LEO • LY • Slightly cooler stars appear white NX • Intermediate stars (like the Sun) glow yellow • Lower-temperature stars appear orange • 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 N BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT www.Astronomy.com/starchart. APRIL 2021

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