2022-10-Astronomy

SRPEEPCOIARLT THE COMING ERA OF SPACE EXPLORATION p.12 OCTOBER 2022 The world’s best-selling astronomy magazine SEE JUPITER www.Astronomy.com Vol. 50 • Issue 10 AT ITS BEST p.28 BONUS OUR ANNUAL ONLINE STAR PRODUCTS CONTENT ROUNDUP p.50 CODE p. 3 PLUS OBSERVE FALL’S BEST DEEP-SKY OBJECTS p. 45 10 MUST-SEE ASTRO PLACES p. 40 BOB BERMAN ON SOLAR FILTERS p. 11

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Online Content Code: ASY2210 OCTOBER 2022 Enter this code at www.astronomy.com/code VOL. 50, NO. 10 to gain access to web-exclusive content 40 ON THE COVER Dunes in the solar system — like this field inside Victoria Crater on Mars — hold secrets to planetary evolution and atmospheres. NASA/ JPL-CALTECH/UNIVERSITY OF ARIZONA/CORNELL/ OHIO STATE UNIVERSITY FEATURES 32 45 COLUMNS 12 Sky This Month See fall’s best Strange Universe 11 Messier objects Oh, the spaces we’ll go The planets get busy. BOB BERMAN Take in 20 sights in just one In the second age of MARTIN RATCLIFFE AND night. MICHAEL E. BAKICH Observing Basics 58 exploration, future astronauts ALISTER LING will capture breathtaking vistas 50 GLENN CHAPLE no earthbound photographer 34 could ever dream of. Our 12th annual Secret Sky 59 Star Dome and Star Products SETH SHOSTAK Paths of the Planets STEPHEN JAMES O’MEARA Astronomy scoured the market 20 COVER STORY RICHARD TALCOTT; in search of the 35 best new Binocular Universe 60 ILLUSTRATIONS BY ROEN KELLY and unique astro products. Dunes of PHIL HARRINGTON the solar system 40 PHIL HARRINGTON 7 From Mars and Venus to Pluto 10 must-visit 62 and Titan, these windblown astro destinations QUANTUM GRAVITY features are starting to tell their Ask Astro story. NOLA TAYLOR TILLMAN These museums, observatories, Everything you need to and telescopes should be on Speedy giants. know about the universe 28 every enthusiast’s travel list. this month: JWST releases its first images Hail to the king CAITLYN of the Cosmic Cliffs, BUONGIORNO Stephan’s Quintet, and This month is a great beyond. opportunity to see Jupiter at its best. MICHAEL E. BAKICH IN EVERY ISSUE ONLINE My Science Trips and Dave’s Picture of From the Editor 4 FAVORITES Shop Tours Universe the Day Astro Letters 6 The inside Gorgeous New Products 61 Go to www.Astronomy.com Perfect gifts for Travel the world scoop from photos from Advertiser Index 61 your favorite with the staff of the editor. our readers. Reader Gallery 64 for info on the biggest news and science geeks. Breakthrough 66 Astronomy. observing events, stunning photos, Astronomy (ISSN 0091-6358, USPS 531-350) is published monthly by Kalmbach Media informative videos, and more. Co., 21027 Crossroads Circle, P. O. Box 1612, Waukesha, WI 53187–1612. Periodicals postage paid at Waukesha, WI, and additional offices. POSTMASTER: Send address changes to Astronomy, PO Box 8520, Big Sandy, TX 75755. Canada Publication Mail Agreement #40010760. W W W.ASTRONOMY.COM 3

FROM THE EDITOR A new era in astronomy Editor David J. Eicher Assistant Design Director Kelly Katlaps The first five released In mid-July 2022, the astronomy images from the world was turned on its ear by a first EDITORIAL James Webb Space release of five images from the James Senior Editor Mark Zastrow Telescope, including Webb Space Telescope (JWST). Launched on Production Editor Elisa R. Neckar this shot of galaxy Christmas Day 2021, the telescope represents Senior Associate Editor Alison Klesman cluster SMACS 0723, a giant leap in sophistication over its predeces- Associate Editor Jake Parks have the astronomy sors. Webb’s primary mirror is a 6.5-meter Associate Editor Caitlyn Buongiorno world electrified. (21 feet) diameter reflector composed of 18 Editorial Assistant Samantha Hill hexagonal segments, each coated in gold. As NASA, ESA, CSA, AND STSCI expected, its first images confirmed that we ART are now in a new era of astronomy, one that we Illustrator Roen Kelly hope will deliver countless discoveries. Production Specialist Jodi Jeranek The night before the full release, President Joe Biden and Vice President Kamala Harris CONTRIBUTING EDITORS released the first image, the deepest shot of Michael E. Bakich, Bob Berman, Adam Block, the universe ever taken to date. Depicting the Glenn F. Chaple Jr., Martin George, Tony Hallas, galaxy cluster SMACS 0723 in the southern constellation Volans, Phil Harrington, Korey Haynes, Jeff Hester, Alister Ling, the image reveals incredible gravitational lensing of distant proto- Stephen James O’Meara, Martin Ratcliffe, Raymond Shubinski, galaxies. The result is the sharpest view of the most distant galaxies Richard Talcott we have yet seen, objects that accreted a few hundred million years after the Big Bang. EDITORIAL ADVISORY BOARD Rather than a pretty picture, the spectrum of a nearby gas giant Buzz Aldrin, Marcia Bartusiak, Jim Bell, Timothy Ferris, exoplanet, WASP-96 b, revealed the most incredible news of that Alex Filippenko, Adam Frank, John S. Gallagher lll, day — the detection of water vapor in the planet’s atmosphere. Daniel W. E. Green, William K. Hartmann, Paul Hodge, Some 1,150 light-years away lies a world that may well be suitable Edward Kolb, Stephen P. Maran, Brian May, S. Alan Stern, atmospherically for living beings. James Trefil A longtime favorite of backyard astronomers, galaxy group Stephan’s Quintet, was another feature. Tidal interactions between Kalmbach Media the galaxies were suddenly crystal clear, as if putting on a pair of glasses from our previous best view. Chief Executive Officer Dan Hickey The Southern Ring Nebula gave us the most distinctive look to Chief Financial Officer Christine Metcalf date at a planetary nebula, foreshadowing our Sun’s future. Six or Senior Vice President, Consumer Marketing Nicole McGuire 7 billion years from now, our solar system will dissipate away in a Vice President, Content Stephen C. George cloud of cosmic soot that reveals the Southern Ring. Vice President, Operations Brian J. Schmidt And there was also a stunning portion of a nebula in Carina — Vice President, Human Resources Sarah A. Horner not the Carina Nebula itself, but NGC 3324, a glorious star-forming Circulation Director Liz Runyon region. The image was just jaw dropping, and left us wanting more. Director of Digital Strategy Angela Cotey Welcome to a new era of astronomy. The deluge of images and Director of Design & Production Michael Soliday discoveries will now keep us busy, and excited, for years to come. Retention Manager Kathy Steele Single Copy Specialist Kim Redmond Yours truly, ADVERTISING DEPARTMENT Follow the David J. Eicher Advertising Representative Kristi Rummel Dave’s Universe blog: Editor Phone (608) 435-6220 www.Astronomy. Email [email protected] com/davesuniverse FOLLOW ASTRONOMY Follow Dave Eicher RETAIL TRADE ORDERS AND INQUIRIES on Twitter: Selling Astronomy magazine or products in your store: @deicherstar Phone (800) 558-1544 Outside U.S. and Canada (262) 796-8776, ext. 818 Fax (262) 798-6592 Email [email protected] Website www.Retailers.Kalmbach.com CUSTOMER SALES AND SERVICE Phone (877) 246-4835 Outside U.S. and Canada (903) 636-1125 Customer Service [email protected] CONTACT US Ad Sales [email protected] Ask Astro [email protected] Books [email protected] Letters [email protected] Products [email protected] Reader Gallery [email protected] Editorial Phone (262) 796-8776 For reprints, licensing, and permissions: PARS International at www.parsintl.com Copyright © 2022 Kalmbach Media Co., all rights reserved. This publication may not be reproduced in any form without permission. Printed in the U.S.A. Allow 6 to 8 weeks for new subscriptions and address changes. Single copy: $6.99 (U.S.). 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ASTRO LETTERS We welcome Humanity in Science Antares is your comments located in the at Astronomy Letters, As I slid your July issue from the mailbox, my first constellation P.O. Box 1612, reaction was, “Art? That’s not what I’m subscribing to Scorpius, and it Waukesha, WI 53187; Astronomy for!” However, it took only a moment’s is one of many or email to letters@ reflection to replace that thought with one of apprecia- real stars astronomy.com. tion and agreement. It is our dreaming and reaching mentioned in Please include your out for what we cannot yet touch that has pioneered Star Trek. ESO/ name, city, state, and country. Letters may our voyages to the planets and beyond, and our tech- M. KORNMESSER be edited for space nology will always trail in the wake of those dreams. and clarity. As I turned the first pages, I was deeply touched by Highly Illogical Marilynn Flynn’s “Shamshu Sojourn,” depicting two astronauts holding hands as they view the jovian vista In Michael Bakich’s article, “An Observer’s Guide to before them. If we do not bring our full humanity with Star Trek” (May 2022), he failed to mention an obvi- us as our science takes us to the stars, then what’s the ous observable: the star Antares, in the constella- point? — John Cimbaro, Lake Worth, FL tion Scorpius. Lieutenant Uhura performed “Beyond Antares” in two episodes of The Original Series: “The Live Long and Prosper Conscience of the King” and “The Changeling.” The Star Trek article by Michael Bakich was fantastic. I — Rebecca Unger, Joshua Tree, CA always wondered if the shows used real names of stars and planets. I liked how he blended the technical infor- Erratum mation with the uses in the sci-fi series. The star maps were great, too. And I just have to get those postage In Bob Berman’s June column, a word was unintention- stamps. — Paulette Jones, Edgewood, MD ally dropped during editing. The second-to-last para- graph should have read “Beyond that, according to ideas from Stephen Hawking, John Wheeler, and other theo- retical physicists, a past that is not set in stone can’t be entirely ruled out.” ECLIPSE ESSENTIALS Get everything you need to learn about eclipses past, present, and future! Shop Today at: MyScienceShop.com/EclipseShop Sales tax where applicable. While supplies last. P40395 6 ASTRONOMY • OCTOBER 2022

NASA, ESA, CSA, STSCI QG QUANTUM GRAVITYEVERYTHING YOU NEED TO KNOW ABOUT THE UNIVERSE THIS MONTH SNAPSHOT THE DEEPEST INFRARED VIEW EVER ON JULY 11, President Joe Biden pre- sented the first science image from the James Webb Space Telescope (JWST) in a press briefing. It is the deepest infrared shot ever taken, showing a galaxy cluster called SMACS 0723. Some 4.6 billion light- years distant, this cluster is acting as a gravitational lens, revealing (and distorting) galaxies behind it. Due to their extreme distances, these ancient background galaxies are heavily redshifted, appearing like bright orange-red tadpoles in a cosmic whirlpool. Whereas the Hubble Space Telescope required weeks to take such deep-field shots, JWST needed only 12.5 hours to grab this view of SMACS 0723. And it’s more than just a pretty picture: Researchers were even able to determine the basic chemical composition of a 13.1-billion-year-old galaxy (below) in the background, the farthest ever characterized. — CHRISTOPHER COKINOS WWW.ASTRONOMY.COM 7

QUANTUM GRAVITY JWST STUNS WITH FIRST SCIENCE After more than two decades President Joe Biden and Vice President (which operates JWST), the Canadian and $10 billion — and surviving Kamala Harris. The rest — images Space Agency, and the European Space a 2011 Congressional effort to kill of three targets and an exoplanetary Agency. Their subjects represent a the project — the James Webb Space atmosphere spectrum — were released range of the types of targets that JWST Telescope (JWST) has finally delivered July 12 during an hour-long broadcast will investigate throughout its mission: its first batch of science images. And, on NASA TV featuring an elated a galaxy cluster, two nebulae, a tight simply put, wow. science team. group of interacting galaxies, and a The first image, of galaxy cluster and strange exoplanet in our Milky Way. gravitational lens SMACS 0723, was The photos were selected by a team of unveiled July 11 at a briefing with U.S. representatives from NASA, the Space JWST is the most powerful space Telescope Science Institute in Baltimore telescope ever built, with a 6.5-meter 8 ASTRONOMY • OCTOBER 2022

IMAGES NASA’s next-generation observatory is now operational. COSMIC CLIFFS Nevertheless, JWST has performed flawlessly. That’s very good news: The Carina Nebula is a stellar nursery Unlike Hubble, which resides in low forming massive stars some 7,600 light- Earth orbit, JWST is too far away for years away. JWST’s image of a portion of servicing. Mission engineers say the the nebula captures a brown bank of gas observatory has enough fuel to last 20 and dust with the appearance of a ridge, years — but if it breaks down, that’s it. silhouetted against the starry sky behind it. Nicknamed the Cosmic Cliffs, the image In other words, a great deal is reveals hundreds of stars never before riding on this dream instrument. seen by human eyes. That’s because JWST Researchers around the world plan to is built to detect infrared light, which use JWST to study everything from penetrates gas and dust. The unparalleled the evolution of the early universe view shows gas congealing to create to potentially habitable exoplanets. stars and jets of energy sculpting the This first set of observations, which surrounding nebula; these jets aid star were released to the astronomical formation in some places and slow it in community in raw form July 13, others. — C.C. are the beginning of science returns that promise to revolutionize many Dec. 25, 2021, JWST has had no major aspects of astronomy for decades issues. One event, however, has triggered to come. much analysis: In May, a mirror segment was struck by a micrometeroid. Such “Now we’ve demonstrated that this impacts are inevitable, but this one was telescope can do what we set out to larger than expected. The performance do, and even better in some cases,” hit from the single impact is measurable, said Amber Straughn, JWST’s deputy but small — still well within the design project scientist for communications, specifications. Only time will tell whether at a press conference after the images JWST was simply unlucky to suffer were revealed. “Astronomers are ready such a hit early in its life or if it is more for this data. We’ve been waiting a susceptible to impacts than predicted. long time.” — C.C. mirror made of 18 gold-plated hexagons, NASA, ESA, CSA, STSCI a tennis-court-sized sunshield, and NASA, ESA, CSA, STSCI four high-tech instruments working in visible and near- to mid-infrared Steam world wavelengths. It orbits the Sun at the L2 Lagrange point, where the combination The first of JWST’s exoplanetary targets was the gas giant WASP-96 b, which of gravitational forces from Earth and orbits a star roughly 1,150 light-years away in the constellation Phoenix. JWST the Sun keep it in a relatively stable observed the planet as it crossed in front of its host star, as it does every 3.5 position. days. By analyzing the starlight that streamed through the planet’s atmosphere, scientists uncovered preliminary evidence of water vapor, suggesting that Since its launch from French Guiana WASP-96 b features clouds and hazes. — C.C. 9

QUANTUM GRAVITY Celestial NASA, ESA, CSA, STSCI (2) DYING STAR’S FINAL ACT dance NASA, ESA, CSA, STSCI JWST took two images of the Southern Ring Nebula, this one in mid-infrared and AT ONE-FIFTH THE MOON’S another in near-infrared light (page 66). This shockingly detailed view of DIAMETER, this near-infrared the object — which looks a bit like an amoeba or an algae bloom — reveals, image (right) of Stephan’s for the first time, the dim star responsible for the planetary nebula. At Quintet occupies the widest the center lies a white dwarf and a brighter companion, their tight orbit view yet released from JWST. stirring the cloud of gas and dust, producing the strange patterns. By using The leftmost galaxy (NGC 7320) resides only 40 million JWST to monitor the light-years away, while the interplay of starlight, other four (from top: NGC 7319, gas, and dust in this NGC 7318B, NGC 7318A, NGC system, scientists will 7317) are some 290 million gain a much better light-years distant. sense of the dynamics of dying stars, as JWST caught astounding well as the planetary detail at near-infrared wave- nebulae they produce. lengths: Individual stars clearly appear in NGC 7320. In the mid- — C.C. infrared (above), shock waves ripple through the galaxies as NGC 7318B bulldozes through the cluster. And at the bright heart of NGC 7319, heated material falling into a supermas- sive black hole at the center shines some 40 billion times brighter than the Sun. The data reveal new information about the temperatures and motions of this glowing gas that will help astrophysicists better under- stand what happens around black holes. — C.C. 10 ASTRONOMY • OCTOBER 202 2

STRANGE UNIVERSE Seeking shade recent study by researchers at the School of Optometry and Vision Science in Waterloo, Ontario, and Sydney, Let’s settle the debate on which solar filter to choose. as well as Rick Fienberg of the AAS. Published last September in The Astronomical Journal, its evaluations of dozens of solar filters “support the use of welding filters between the shades of 12 and 16.” So, you can safely count on shades 12, 13, and 14. (You wouldn’t want a 15 or 16 because the image is too dark.) And yet you can still find websites warning to only use a shade No. 14. A few also advise against looking at the Sun for more than 15 seconds. One site cautions that even through a dark No. 14 filter, you should only observe the Sun when it’s totally eclipsed. Eclipse-savvy readers will laugh at that one, since if you actually followed that last bit of advice, you’d see complete black- ness and miss everything. Moreover, The Astronomical Journal paper notes that the government standard all eclipse filters (including the brightest safe welders’ ABOVE: Recent It’s now only 1½ years until the next filter, shade No. 12) must research confirms meet allows for more than that viewing the 25,000 seconds of continu- partial phases of a U.S. total solar eclipse. On April 8, ous Sun viewing. That’s 6.9 solar eclipse through 2024, the Moon’s shadow will head hours! welders’ glass in north out of Mexico to throw parts of 15 U.S. states So despite much online non- shade 12 or darker is safe — but which and a few Canadian provinces into full totality. It’ll be sense, it’s scientifically settled that provides the best you can safely either purchase any Sun filter experience? MROTCHUA/ 20 years before we get another one. that meets international standard ISO 12312-2, or else use a shade 12, 13, or 14 DREAMSTIME Solar totality is almost surely the greatest Solar welding filter. But which shade is best? natural spectacle the eye can behold. It lasts CENTER: You’ll also Glad you asked. During the last eight need a filter for only a few minutes, but for an additional two totality is years of total eclipse tours, we’ve offered viewing all phases hours, the event’s partial phases offer them- guests a choice between a 12 and a 14 the day of an annular eclipse, selves for observers who have eye protection. almost before the event. Hundreds of people com- as the Moon doesn’t surely the pared the two. The result: Nobody wanted a cover the entire solar For my first totality, at Virginia Beach in greatest disk. HAJIME NAGAHATA 1970, I bought black-and-white film, which I fully exposed and then developed. Two layers natural (CC BY 2.0) of that created a safe filter. But no more — spectacle shade 14. The view, they all felt, was unpleas- film, if you even remember what that is, no the eye can antly dark. longer reliably contains the silver emulsion that’s vital for blocking harmful rays. behold. Still, my opinion is that 12s, while safe, give a slightly glaring image. Not bother- When I started leading eclipse tours in the some, just not ideal. So I ordered a bunch of ’80s, I always provided shade No. 12 welders’ the rare 13s and we used those for the 2019 filters. Then, when the internet arose and some websites Chile solar totality. Perfection at last! But was it just claimed only the darker shade 14 was safe, I’d bring a our opinion? bunch of those along, too. We’ll get to aesthetics in a This past February, I sent a 12, a 13, and a 14 filter minute, but first let’s look at the all-important issue of to this magazine’s staff and asked if they’d look at the BY BOB BERMAN safety. Sun and vote on which image they liked best. The Bob’s recent book, At https://eclipse2017.nasa.gov/safety, NASA says result: They prefer the 13s, too. Earth-Shattering “The only [welders’ filters] that are safe for direct view- Now you know what to buy if you want to follow the (Little, Brown and ing of the Sun with your eyes are those of Shade 12 or Company, 2019), higher.” The American Astronomical Society (AAS) “in” crowd. explores the greatest used identical phrasing before that same totality. cataclysms that have BROWSE THE “STRANGE UNIVERSE” ARCHIVE shaken the universe. Those wanting technical information can turn to a AT www.Astronomy.com/Berman WWW.ASTRONOMY.COM 11



OH, THE SPACES WE’LL GO In the second age of exploration, future astronauts will capture breathtaking vistas no earthbound photographer could ever dream of. BY SETH SHOSTAK SMALL STEP IN THE LAST DECADES OF THE 15TH CENTURY, ABOVE: Buzz Aldrin took this Western Europe experienced a metaphorical Big Bang — a sud- famous image of his bootprint den explosion of geographical knowledge that was later dubbed on the Moon as part of an the Age of Discovery. Improved sailing ships carried profit- experiment led by scientists minded crews into uncharted seas, revealing the full extent of studying the mechanics of Earth. lunar soil. NASA In 1450, world maps drawn in Europe had only a few sketchy FIRST MEN indications of West Africa and the Far East. But over the span of a single human lifetime, geographic knowledge grew faster LEFT: Neil Armstrong snapped than bamboo. Our understanding of where and how the conti- this iconic portrait of Buzz nents were arranged was completely transformed. Explorers Aldrin standing on the Moon and merchants visited and mapped the majority of the temper- next to the Lunar Module Eagle. ate world’s coastlines. Globes became something more than Armstrong is visible in the minimally useful household furniture. reflection on Aldrin’s helmet, making this the only photo The Age of Discovery was the product of a special time, a staged to show the duo period in European history when it was barely possible — and together on the lunar surface. still highly dangerous — to chart the world. It could not have happened earlier because it depended on improvements in NASA shipbuilding that allowed repeated crossings of the oceans. A century later, with yet better technology, replicating these accomplishments became trivial. There is always a “right time” WWW.ASTRONOMY.COM 13

the century, we will enter close-up photos of our natu- CLOCKWISE a second Space Age: an ral satellite. The standouts FROM LOWER LEFT: extended period during in this collection include which humans will under- the imprint of a boot in EARTHRISE take our own exploration of the lunar dust and Neil the solar system. As human- Armstrong’s full-body One of the most ity develops the ability to portrait of Buzz Aldrin in influential photographs travel to and wander around ever taken, Bill Anders’ nearby worlds, we will see Earthrise from Apollo 8 and photograph spectacular captures our planet as, in landscapes and novel views the words of crewmate that will come to define our Jim Lovell, “a grand oasis nearby space environment. in the big vastness of The solar system will be space.” NASA captured in a series of iconic scenes, a collection of CHARTED images that will shape how we think of our own galactic The Camaldolese monk neighborhood. Fra Mauro created this mappa mundi (medieval But wait! Hasn’t that European world map) already occurred? Haven’t around the year 1450. It we already seen what the measured nearly 8 feet solar system has to offer? (2.4 m) on each side and is one of the most We’ve made a start, significant maps in the beginning with the Apollo history of cartography. Program and its beguiling, The map was oriented south-up; flip it upside down for a more familiar view. MUSEO CORRER LUNAR PEAKS Montes Apenninus, or the Apennine Mountains, lie on the southeastern border of Mare Imbrium. They contain Mount Huygens, the highest mountain on the Moon. NASA/JPL-CALTECH/ARIZONA STATE UNIVERSITY ALPINE EXCURSION On Apollo 15, astronauts David Scott and Jim Irwin scaled the lower slopes of Mount Hadley Delta in the Apennines with the lunar rover, driving to a height of roughly 300 feet (90 m) above the surrounding terrain. NASA/MIKE CONSTANTINE for pioneers who, by defini- tion, work at the edge of the possible. While you may think that, logically speaking, there can only be a single Age of Discovery, that’s not true. We are currently con- cluding the first Space Age, marked by landings on the Moon and robotic forays to other worlds. By the end of 14 ASTRONOMY • OCTOBER 2022

his helmet and space suit. ability to travel to other solar moneymakers in the gift numbers. But that’s a sterile Behind Aldrin are the dusty system worlds, we will inevi- shops of planetariums and view of science, akin to pre- hills of what he called a tably stumble into vistas that space centers. tending that styling has no “magnificent desolation.” It will resonate with us: stark relevance to automobiles. was a visual statement that panoramas that capture a Lunar landscapes humans had made their first feeling of astonishment and As an example of how art foray into the final frontier. images that don’t just show It might seem silly to assign matters, consider the photo- us a landscape, but take us much worth to the emotional graph made by Bill Anders We still don’t have equiv- there. This, the “visual power of photos made by Dec. 24, 1968. He and fellow alent photos of humans on poetry” of exploration, may future astronauts. Scientists astronauts Frank Borman Mars, although orbiters and not do much to further our will argue that only experi- and Jim Lovell were orbiting rovers have given us close-up scientific understanding. mental results count, and the Moon — the first views of the Red Planet’s But it will surely continue beautiful pictures are little humans to do so — on topography for half a cen- to stoke our enthusiasm more than frill. If cameras Apollo 8. As they rounded tury. To those you can add for venturing beyond our are part of an experiment, the lunar farside, Anders a few detailed photos of natal world. The best of they’re valuable only inso- saw the disk of Earth edging a small patch of Venus, these images will become far as the resulting pictures above the horizon. Sensing various flyby portraits of tokens of our wanderlust can be quantified — accu- a “Kodak moment,” he fragile-looking asteroids, — not to mention reliable rately measured, scaled, and grabbed some color film, and, of course, broad-brush calibrated to produce useful loaded it into his modified views of planets and satel- Hasselblad 500 camera, and lites taken from distances snapped away. The resulting of a few thousand miles or photo, Earthrise, is one of more. Thumb through any the most recognizable pic- astronomy textbook and you tures ever taken. It is more will see all of these things. than a striking photo of two worlds. It shows Earth as a However, with the excep- jeweled ball, lost in an ocean tion of photos snapped by of empty darkness. astronauts, our pictorial inventory of the solar system Although about 6,000 has been made with the dead photos were snapped by the eyes of cameras bolted to favored few chosen to make uncrewed spacecraft or rov- giant leaps for humankind, ers. Yes, they can document these images were as much a scene, but they can’t gauge documentation as artistry. the emotional tug of the pic- But imagine the future, the tures they make. pictorial possibilities if you dared to hie yourself up But as we develop the

Mount Huygens, the Moon’s mountain, you won’t surveil Martian terrain Mons, lined up like the stars tallest peak. It’s an 18,000- a huge swath of territory. On of Orion’s Belt (or, if you foot (5,500 meters) climb, Earth, the horizon seen from It’s safe to say that the best prefer, the large pyramids at and you’ll require a special an 18,000-foot (5,500 m) Moon pictures are still to Giza) and spaced by roughly suit and an oxygen supply mountain is about 164 miles be made. But if you find the 500 miles (800 km), one to (it will be BYOO no matter (264 kilometers) away. On idea of Moon photos too the next. This set of volcanic where you venture beyond the Moon, it is 86 miles old-timey, there’s always pinnacles would make a Earth). (138 km). On smaller worlds, Mars. Imagine recording lovely, iconic composition it will look as if there’s an Mars’ crevassed and cracked from orbit, looking obliquely Mount Huygens rivals edge over which you might terrain as it extends in all down the line at sunrise or Mount Kilimanjaro in fall, especially as the horizon directions from the base of sunset — at least until the height, although it can claim won’t be blurred by haze. the solar system’s highest next global dust storm sets considerably less wildlife. perch, Olympus Mons. That in. If you ventured to their And because Mount would undoubtedly be a pic- summits, you could look Huygens is a member of a ture suitable for framing. down into their central cal- chain, Montes Appenninus, deras — each broad enough there would be satisfying Olympus is an inactive to swallow the New York views of lesser peaks to volcano more than twice the City metropolitan area. either side. There would also height of Mount Everest. Its be vistas across broad, flat highest reaches would offer There’s an alternative to areas, including Mare you the sight of level topog- schlepping a camera to alti- Imbrium, the Sea of Rains. raphy as far as 240 miles tudes where the martian On Earth, the rule of thumb (386 km) away. Given that atmosphere is thinner than is that it takes an hour to this is the tallest mountain the veneer on cheap furni- climb 1,000 feet (305 m). So, in the solar system, however, ture: a descent into the you would need to allow two it may someday become mother of all canyons, Valles days to clamber to the top entirely too popular and, Marineris. This is the only of this dusty massif. like Everest, crowded with “canal” that Percival Lowell climbers. could possibly have seen Another point: Because with his 24-inch refractor in the Moon has a diameter Roughly a thousand Flagstaff more than a cen- that’s little more than ¼that miles from Olympus are tury ago. It’s well-known for of Earth, the horizon will three other volcanoes being five times deeper than be closer. Even from a on Mars’ Tharsis Bulge: Ascraeus, Pavonis, and Arsia 16 ASTRONOMY • OCTOBER 2022

CLOCKWISE the Grand Canyon and lon- enough to direct you to some Distant worlds FROM LOWER LEFT: ger end-to-end than Route of the best picture opportu- 66. This might strike space nities. And rovers trundling Before quitting the inner THARSIS BULGE agency bureaucrats as terrain across the dusty regolith solar system, let’s consider too risky for a rover. have made snaps that are vistas that await anyone Olympus Mons dominates comparable in detail and brash enough to challenge the foreground of this But if you’re willing to dynamic range to those the torrid and foggy envi- image taken by ESA’s Mars find your way to the floor of made with a cellphone. Even ronment of Venus. Earth’s Express orbiter, with this canyon, you could take though rovers have yet to sister planet is swathed in Ascraeus, Pavonis, and some unique photos by investigate much Red Planet an atmosphere of uninviting Arsia Mons lurking in the standing near one of acreage, their photos have carbon dioxide, seasoned background. ESA/DLR/FU BERLIN/J. its 4-mile-high (6.4 km) already given an idea of the with clouds of sulfuric acid. walls. Positioning yourself in lay of the land. With a sur- The cloud layers begin in COWART, CC BY-SA 3.0 IGO the middle of the main chan- face sculpted and shaped by earnest 30 miles (48 km) nel might be disappointing, 40 million centuries of fast above the planet’s surface GRANDEST CANYON however, as the walls would winds, this modestly-sized and extend to an altitude be some 20 miles (32 km) world is undoubtedly a of about 56 miles (90 km). There would be no away and difficult to discern. photographic paradise, a Within the main cloud shortage of stunning vistas Of course, there would planetwide national park. deck, visibility in this pea- of Valles Marineris for any always be the novelty of step- soup atmosphere would be astronauts who explored ping in a puddle or two of it. This oblique view was liquid water, made possible constructed from imagery by the higher atmospheric and terrain data pressure on the canyon floor. (exaggerated by a factor of four) from ESA’s Mars In fact, when considering Express mission. ESA/DLR/FU where award-winning photos might be taken, Mars is per- BERLIN (G. NEUKUM), CC BY-SA 3.0 IGO haps too easy. Images from the orbiting $40 million AERIAL TOUR HiRISE (High Resolution Imaging Science Experiment) The walls of Valles camera show details down to Marineris lie roughly a foot (0.3 m) in size, good 100 miles (160 km) apart in this high-altitude view generated with data from NASA’s Mars Odyssey mission. NASA/JPL/ARIZONA STATE UNIVERSITY MODEST MOON Saturn’s 72-mile-wide (116 km) moon Epimetheus appears to hover above the planet’s A and F rings, cutting across the frame. In the background lies the hazy disk of Titan, Saturn’s largest moon. NASA/JPL/SPACE SCIENCE INSTITUTE

limited to a few miles — if in the rearview mirror, all the jovian and saturnian CLOCKWISE there were anything to see hard-surface real estate will systems. Both are unques- FROM LOWER LEFT: up there in the first place. be limited to asteroids, plan- tionably spectacular, even All of which suggests that etesimals, or moons. But the though photos of them have HAZY CONDITIONS until you get down onto the gas giants are no less stun- all been made from at least crispy surface, photos will be ning. Beginning about 50 2,000 miles (3,200 km) above ESA’s Huygens probe tediously blank and bland. years ago, our spacecraft their colorful atmospheres. captured these started showing us views of panoramas of Titan as But there’s an exception Jupiter and Saturn are it descended through to that. Get yourself a dozen each accompanied by ragtag its atmosphere Jan. 14, or so miles above the main hordes of moons, many of 2005. ESA/NASA/JPL/UNIVERSITY layer of clouds, and you will which have their own behold a spectacular vista personalities. A pleasing pic- OF ARIZONA at sunrise or sunset. Lying torial arrangement of one or underneath your photo- more of Saturn’s moons TITAN FIRMA graphic perch will be a together with the planet and hummocky, yellow-white its ring system spanning the When Huygens touched carpet — the roof of the frame would be a real con- down on Titan’s surface, cloud deck — stretching a versation starter in your it sent this image of few hundred miles in every game room. what may be a dry direction. This is the reality riverbed where methane of a runaway greenhouse For astronauts seeking sometimes flows. The effect, seen up close and solid ground, the choicest ground — and the personal, and unrivaled aesthetic pickings in these pebbles that litter it — anywhere else in the solar distant realms are hard to consist of a mixture system (as yet). guess. This is largely because of water ice and the smallest details we’ve hydrocarbon ice. NASA/JPL/ Heading out into the been able to record of objects solar system, once Mars is beyond the asteroid belt are ESA/UNIVERSITY OF ARIZONA typically 0.5 mile (0.8 km) in 93 miles (150 km) size or larger. (Let’s except RING LIGHT the ground-level pictures of Titan made by the Huygens The Sun provides probe in 2005.) dramatic backlighting for Saturn and its rings in But among the features this photograph taken by we have seen, perhaps the NASA’s Cassini probe in most alluring are the ice 2013. Venus, Earth, and mountains on Pluto, imaged Mars appear as mere by the New Horizons space- dots in the image. NASA/ craft. These hard-as-granite peaks are large enough that JPL-CALTECH/SSI you could see them from the vicinity of Pluto’s moon FRIGID WORLD Charon with a decent pair of binoculars. If you can with- Pluto’s majestic frozen stand Pluto’s nippy tempera- mountains tower up to tures (a bracing –387 degrees 11,000 feet (3,500 m) Fahrenheit [–233 degrees above the icy fields of Celsius]), you might go Sputnik Planum in this down to its surface to line image taken by NASA’s up a telephoto shot of a few New Horizons mission. mountains framing Charon, hanging low in Pluto’s black NASA/JHUAPL/SWRI sky. Charon would be about 9 miles (15 km) seven times the apparent diameter of our own Moon. 1.2 miles (2 km) As a somewhat more 0.25 mile (0.4 km) ambitious photographic 18 ASTRONOMY • OCTOBER 2022

Mars Venus Earth and the Moon effort, consider an expedi- The human touch our cosmic neighborhood their earthbound handlers. tion to roughly 2 billion from afar. After all, most Arguably better pictures can miles (3.2 billion km) above I’ve heard space aficiona- astronauts insist on round- be made by on-the-spot the ecliptic plane in which dos, including scientists, trip tickets, something that humans with an aesthetic the planets orbit. Bayonet insist that the future of the robotic craft never do. bent. More than 60 years a workaday lens onto your space exploration won’t ago, the Space Age paintings camera and aim it down- include much of the free- That sounds reasonable, by Chesley Bonestell ward. You should be able to wheeling human wander- at least, at first. But try inspired movies, magazine see the Sun and all the plan- ings described here. These walking into a sixth-grade series, and, ultimately, an ets out to Saturn. They’ll proudly pragmatic folk classroom and asking how entire generation of young- appear only as bright dots. maintain that they’re only many of the kids are keen sters who wanted to go to (The Sun will be a fat bright being realistic when they to go into space. You’ll find other worlds. They still dot!) But the fact that the argue that the solar system a lot of takers. want to go. image is real, and not a cut should be explored and in a book, should lend it a photographed by robots, not Then ask how many pre- There’s something funda- certain je ne sais quoi. people. Humans should sim- fer to become earthbound mentally different about ply stay at home and view engineers, building robotic witnessing nature in person, spacecraft. Many of those for otherwise how do you hands will go down. Yes, justify muscling a 12-inch space exploration is a hard, Dobsonian out on a cold expensive, and dangerous night to spend hours squint- business, so it’s only natural ing through a viewfinder? to champion a very practical Especially when you could approach — namely, that we find a better picture more tether humans to terra firma comfortably (and with con- and leave the exploring to siderably less expenditure of the machines. The latter time, money, and effort) don’t require heavy and online? complicated life support systems, or shy away from It’s the romance of going mortal danger. somewhere — to step into a time machine that can take But clearly, robotic explo- you millions of miles into ration is not the same. the velvet voids of space to Photos made by robot cam- give you a view that’s more eras may have tremendous than just an image, but an fidelity, but the only artistry experience. they have is that arranged by Seth Shostak is senior astronomer at the SETI Institute and host of the weekly podcast Big Picture Science. WWW.ASTRONOMY.COM 19

The floor of Mars’ Victoria Crater contains a small field of dunes that appear to ripple up from the otherwise flat, featureless terrain. (As a bonus, the now-defunct Opportunity rover sits just outside the crater rim in the 10 o’clock position on this particular image.) NASA/JPL-CALTECH/ UNIVERSITY OF ARIZONA/CORNELL/OHIO STATE UNIVERSITY

From Mars and Venus to Pluto and Titan, these windblown features are starting to tell their story. BY NOLA TAYLOR TILLMAN D unes of sand sweep across the solar system, building drifts on any world with even the slight- est hint of a breeze. Some look like the features we’re familiar with on Earth, made up of bits of rock or ice, while some appear far more alien, built solely from organic material. From Mars to Pluto to tiny comets, the wide variety of dunes scientists see may help refine outstand- shells, coral, carbonate, volcanic ash, ing questions about how dunes form on and even ice. That means sand can Earth, along with providing information develop and settle not only in beaches about past and present conditions on and deserts but also in the frozen bar- distant worlds. rens of Antarctica. Furthermore, the definition of sand has nothing to do with Studying dune patterns can reveal not composition and everything to do with only insights about a body’s surface com- size and how it is transported: particles position, but also hint at its atmospheric that are small enough and light enough history. Thinner atmospheres make it to be lofted into the air. On Earth, harder to toss particles into the air, so that’s around 0.0025 to 0.08 inch (0.06 ancient dunes can reveal how sand to 2 millimeters) in diameter. On other rained from the sky when thicker gases worlds with less gravity, sand particles blanketed a world. This can be critical can be larger. on bodies like Mars, whose hefty atmo- sphere slowly escaped over time, and So, how do you go from particles of Pluto, whose atmospheric density grows sand to rippling dunes? The key to dunes and shrinks as it travels around the Sun. is wind. “As long as there’s movement of air molecules, we … end up with an How to build a dune aeolean field,” or a landscape sculpted by wind-deposited sand, says Jani On Earth, sand is commonly built by Radebaugh of Utah’s Brigham Young eroding quartz. But it can also comprise WWW.ASTRONOMY.COM 21

University. (Aeolean refers to the Greek A sea of frost-tipped volcanic in origin. Rocky basalt hurled god of wind, Aeolus.) dunes covers the floor of explosively from now long-dead volca- a crater near the north noes eroded to particles some 0.002 to Despite their compositional variety, martian pole. The 0.02 inch (0.05 to 0.5 mm) in diameter dunes on Earth all form under roughly complex patterns of over millions of years. Water, which may the same conditions and are limited pri- ripples and textured have flowed briefly across the surface in marily by gravity, which affects how far terrain are produced the distant past, could have potentially sand can fly. By looking at the wide vari- by seasonal cycles of broken down some of the rocky material ety of dune-covered solar system worlds, frost formation and into sand, but today, wind provides the scientists hope to get down to the nitty- sublimation. NASA/JPL-CALTECH/ most prevalent source of erosion. Wind gritty of how sand dunes form and shift. is inefficient compared to water when it The basic idea is simple: Wind carries UNIVERSITY OF ARIZONA comes to eroding rock into sand, though. sand across the surface, eventually piling That raises the question of how old mar- it up in dunes. But the details are where Martian mayhem tian sand is: Did it all form when water things get messy. Is the sand following a flowed across the surface, or is more fluid dynamic model, traveling through In the early 1970s, NASA’s orbiting sand still being created today? At least the air much as it swims through water Mariner 9 seemed to show Mars as a some of the sand is recycled as weathered to create water-sculpted dunes? Or does dead, unchanging world similar to Earth’s particles form sedimentary rocks that are it obey an impact mechanism model, Moon. Only when the Viking missions later turned back into sand — Diniega where the first grain of sand lifted by the began capturing higher-resolution images speculates most of it is — but after sand wind kicks up other grains that go on to of the Red Planet a few years later did the particles have collided enough times, kick up even more? views reveal active processes, including they break down into dust, which geolo- sand dunes. gists generally define as particles smaller According to Serina Diniega, a than about 0.0025 inch (0.06 mm). So, researcher at the Jet Propulsion Most martian sand appears to be the fact that Mars still has sand suggests Laboratory in Pasadena, California, the either low dune motion (few collisions) two models are difficult to distinguish or that there is more ongoing erosion between on Earth because their predicted than currently estimated. results look so much alike. But altering the air pressure and gravity — by, say, In 2016, NASA’s Curiosity rover building dunes on another world — captured close-up images of dunes, should provide greater insight into which model is correct. “Finding dunes on other bodies, in other conditions, helps discriminate between models that we would not be able to test between on Earth,” she says. Fortunately, there are plenty of dunes in the solar system. SUSPENSION, SALTATION, CREEP Suspension Wind Wind Saltation Creep Sand particles have a characteristic size that allows the wind to pick them up and move them through a series of short bounces, called saltation. Dust particles, which are smaller than sand, move in suspension — the wind picks them up and they remain airborne until it dies down. On the other end of the size spectrum, larger particles creep along the surface, essentially rolling or sliding when blown by the wind without ever being picked up. ASTRONOMY: KELLIE JAEGER

confirming predictions based on the TOP: NASA’s Opportunity rover snapped this false-color image of roughly 3-foot-high (1 m) tendrils planet’s characteristics regarding how extending from dunes in Endurance Crater. The lighter-colored dune crests are covered in finer-grained large sand can grow on the Red Planet. material than the darker, bluish bases, which contain material rich in hematite. NASA/JPL/CORNELL Martian sand is roughly the same size as its terrestrial counterpart, but weaker BOTTOM: In 2017, the Mars Reconnaissance Orbiter imaged this portion of a martian megadune just as gravity allows lighter sand to fly, even northern spring was revving up. Carbon dioxide frost is beginning to sublimate away in the thin atmosphere, in the thin air, and form dunes. revealing the darker sand of the dunes beneath. NASA/JPL-CALTECH/UNIVERSITY OF ARIZONA That flight relies on wind speed: near the martian equator. By comparing atmosphere. Meanwhile, landers and Wind tunnel experiments suggest that images taken more than seven years apart rovers can only provide wind speed getting a grain of sand moving on Mars at two different sites, the team deter- information at ground level; this leaves takes a gust 10 times stronger than mined that these megaripples — which a wide stretch of sky empty of atmo- required for the same grain on Earth. are the largest of dunes at around 3 feet spheric measurements. But once the sand starts moving, it’s eas- (1 meter) in height — edge along at about ier to keep it going, thanks to the planet’s 4 inches (10 centimeters) per year. Ideally, a rover or lander would sit in lower gravity. “The big unknown for one spot and stare at the sand movement Mars is the threshold you need to start Even today, scientists aren’t certain constantly, rather than in timed snap- the movement of sand,” says Simone how strong surface winds are on Mars. shots, Diniega says. That would allow Silvestro, a researcher at the National They have mapped out global wind researchers to ground their models in Institute for Astrophysics (INAF) in Italy. patterns based on the topography and truth. Given that windy, dust-filled air how the landscape has formed, but the has the potential to clog and damage For decades, scientists suspected the bulk of atmospheric measurements for robotic explorers, it would be even better, dunes they saw on Mars were ancient rel- the planet have been made by orbiters, Silvestro says, to send people to the planet ics from a past featuring a thicker atmo- which are limited to observing the upper to measure wind speeds and dune motion. sphere and stronger winds. That changed in 2019, when Silvestro and his colleagues used NASA’s Mars Reconnaissance Orbiter to capture dunes creeping along GETTING A GRAIN OF SAND MOVING ON MARS TAKES A GUST 10 TIMES STRONGER THAN REQUIRED FOR THE SAME GRAIN ON EARTH.

0.6 mile/1 km shows the high temperatures could cause particles to melt together into an unwieldy conglomeration too large to fly in what little wind there is on the surface. It’s also possible that traces of ancient dunes were wiped clean in a planetwide resurfacing event some 500 million years ago. Volcanic eruptions spewed lava across the surface, erasing craters and dunes to create a clean slate only slightly scratched on more recent timescales. If Venus is hiding dunes, they may soon come to light. In 2021, NASA announced two new Venus missions, VERITAS and DAVINCI, while the European Space Agency revealed plans for a third, EnVision. The trio should begin probing the planet in the 2030s. The Magellan spacecraft mapped some 98 percent of the surface of Venus Saturn’s satellite Titan using radar. Small dunelike features, characterized by different reflective properties in the surface terrain, appear in at least two small fields on the planet, With its organic haze and methane lakes, including this portion of Al-Uzza Undae. FROM TOP: NASA PLANETARY DATA SYSTEM IMAGING NODE/USGS; Saturn’s moon Titan is the only world in the solar system besides Earth known to NASA/JPL sustain liquid on its surface. But while researchers predicted its lakes of meth- Vestiges on Venus Magellan mission ane and ethane in the 1980s, windblown mapped nearly the sand dunes were considered unlikely due Often called Earth’s twin, Venus might be entire planet with the planet you would most expect to sport radar, revealing the to the world’s poten- dunes on the surface. After all, a thick first faint hints of two tially sticky sediments, atmosphere can dramatically improve the small dune fields. which are made of tarry odds of sand-lofting winds, and the venu- While scientists have hydrocarbons. sian atmosphere is 90 times denser than speculated radar sig- our planet’s. But though Venus’ upper nals hint to the pres- So it was a surprise atmosphere zips along at a fast clip, sur- ence of centimeters-long “microdunes” in in 2006 when NASA’s face winds creep by at only a few miles per the planet’s southern regions, clear evi- Cassini mission revealed hour. So, dunes appear sparse on Venus. dence of such features remains hidden. aeolian dunes spread across the moon’s mid- But one reason for this paucity may be Additionally, making sand on Venus latitudes. “They’re the lack of good images. Although several is a challenge in itself. That same thick almost a defining fea- missions have been sent to explore Venus, atmosphere dampens the explosive volca- ture of Titan,” says the planet’s thick atmosphere makes nic processes that could create ash to serve Ralph Lorenz, a dune catching a glimpse of the surface — or as sand. And the planet lacks the liquid expert at the Johns surviving on it — even more challenging. water necessary to carve small particles Hopkins Applied Most photos are radar images captured from the rocky surface. Most venusian Physics Laboratory from Earth and from orbiting spacecraft, sand is thought to have formed when in Laurel, Maryland. which aren’t comparable to visual snap- impacts struck the surface and threw up One of the biggest surprises was the shots, such as those scientists have of material. Even if sand forms, research fact that Titan’s dunes stretch across the Mars. In the early 1990s, NASA’s surface in the opposite direction from the usual gentle motion of its winds. It turns out that Titan’s winds briefly reverse their flow and grow stronger during the equinoxes. These backwards seasonal winds are more likely to create dunes than the lighter breezes blowing the rest of the year. While sand on Earth and Mars comes from material worn away with time, Titan’s sand may rain down from the sky. 24 ASTRONOMY • OCTOBER 2022

LEFT: Dunes on Titan (top), mapped via radar by Cassini, appear similar in structure to those formed in Earth’s Namib Desert (bottom). The bright features in the top image are not clouds, but rather terrain that appears lighter in radar imagery. FROM TOP: NASA/JPL; NASA/JSC BOTTOM: This close-up shows a field of longitudinal dunes on Titan. Planetary scientists believe Titan’s dunes could be composed of sticky hydrocarbon sand that may rain down from the sky. UNIVERSITY OF HAWAI’I Tholins, clumps of organic matter whose concerns raise another issue. “It’s a big- rovers tend to avoid dunes, where soft precise composition remains a mystery, ger challenge to get funding to do the sand can bog them down, Dragonfly’s cover the surface of Titan, making up experiments,” she says. ability to soar from one location to the clouds and haze in the moon’s atmo- another will allow it to study numerous sphere. The material may stick together Many questions may soon be surface features — including, Lorenz to form sand-sized particles as it falls answered by NASA’s Dragonfly mission, expects, dunes. from the sky, only to be blown into a flying rotorcraft planned to explore dunes. But how such processes work with Titan in 2034. Horst says Dragonfly Pluto’s icy dunes organic material is not well understood. should deliver “more complex informa- tion about the particles to help find out When NASA’s New Horizons mission “The outstanding question at this how they’re made.” breezed past Pluto in 2015, it revealed a point is whether there is some kind of surprisingly active dwarf planet, rather aggregation process happening to make Because Dragonfly will explore at than the dead world many researchers haze particles stick together, making various altitudes rather than staying expected to lie at the edge of the solar sand-sized particles that way,” says stuck on the surface, the mission will be system. The quick snapshots captured Sarah Horst, a Titan researcher at Johns able to take more detailed readings of the by the spacecraft showed the surface of Hopkins University in Baltimore. atmosphere than are available for other Pluto has been sculpted by ice relatively non-terrestrial worlds. That should help recently, and scientists have identified Alternatively, tholins could form a scientists understand how tholins are a wide variety of geological features. sedimentary layer that is later eroded by blown across the landscape. And while Titan’s flowing liquid. Or the sand could instead be composed of material left behind once that liquid has evaporated, like the ring in a bathtub. Titan’s exotic environment makes determining the details of dune forma- tion difficult. According to Horst, who experiments on tholins in her lab, one of the challenges of understanding the strange substance is trying to figure out how organic material behaves at temperatures on Titan: –297 degrees Fahrenheit (–183 degrees Celsius). “A lot of these compounds we’re interested in are toxic or explosive or both,” she says. While there are plenty of labs capable of handling the temperatures and com- pounds, including Horst’s, the safety Many questions may soon be answered by NASA’s Dragonfly mission, a flying rotorcraft planned to explore Titan in 2034.

Pluto’s tenuous atmosphere, captured here in When New Horizons flew past Pluto in 2015, it those particles are then swept into dunes dramatic backlighting by New Horizons, is likely imaged a geologically diverse world that has by the winds. too thin for its winds to efficiently pick up particles intrigued researchers. This image, one of the from the ground and blow them into dunes. Instead, highest-resolution photos snapped by the Only a portion of Pluto’s surface was researchers speculate that dunes might get their spacecraft, shows a portion of Sputnik Planitia, the imaged and of that, just a small part start as methane from the surface sublimates, western half of the dwarf planet’s famous heart. appears to have dunes. Tefler says this sending material into the air that is then swept Numerous dunelike features appear on the pitted may be thanks to the local landscape. into dunes. NASA/JHUAPL/SWRI nitrogen-ice terrain at lower right. NASA/JHUAPL/SWRI “Circulation models suggest that area we’re looking at there should be the Radebaugh was chatting on Facebook the atmospheric density is so low, your windiest place on Pluto,” he says. “It’s a with fellow planetary scientist Matt ability to transport material decreases,” place that, because of the thermal and Tefler while the first images of Pluto Horst says. So how are the particles tak- pressure-driven properties derived by were released. As they began studying ing that initial jump? the terrain, is likely to promote wind.” the snapshots, dunelike structures in the heart-shaped feature now called Radebaugh and Tefler think the But not everyone thinks there is Tombaugh Regio jumped out at the pair. answer lies in a field of small pits near the enough evidence yet to declare the fea- To Radebaugh, they appeared similar to dunes. Pluto is covered with ice composed tures are dunes. “It’s still an ongoing dunes found in Death Valley, California. of not only water, but also methane, nitro- debate in the planetary geomorphological “It clicked right away: ‘Oh, these are gen, and carbon dioxide. As the methane community,” says Phillipe Claudin, also at dunes,’ ” she says. works its way to the surface, it jumps INAF. Tefler and Radebaugh remain con- from a solid to a gas, throwing methane fident that what they’ve spotted are dunes, They reached out to the New Horizons molecules into the air and leaving the though it will most likely take another team, working with their geologic group small pits. Radebaugh and Teffler think mission to far-off Pluto to confirm the to nail down the landforms. After exam- nature of the features. ining the images in more detail than was available during the initial release, they Common comets found the features bore more than a passing similarity in shape to dunes. The If planetary scientists were surprised dunes also aligned well with wind streaks to find dunes on Pluto, where the identified by other researchers, suggest- atmosphere is thin, they were floored ing the winds that formed the streaks to find them on the tiny Comet blew in the same direction as the winds 67P/Churyumov-Gerasimenko, where that created the dunes. an atmosphere is all but nonexistent. As on other worlds, the biggest chal- Often compared to a rubber ducky, lenge for scientists is to figure out how Churyumov-Gerasimenko has two lobes Pluto generates the initial lift that gets joined together by a neck. This shape is dunes rolling. Pluto’s atmosphere is most likely the result of two separate incredibly thin — likely too thin to pick pieces of early solar system material slowly up particles from the ground. “It’s hard coming together. When the European to actually get the math to work because ONLY A PORTION OF PLUTO’S SURFACE WAS IMAGED AND OF THAT, JUST A SMALL PART APPEARS TO HAVE DUNES.

Space Agency’s Rosetta spacecraft entered about Churyumov-Gerasimenko. “I would Images from NASA’s Galileo spacecraft orbit around Churyumov-Gerasimenko in say what we are seeing is rather generic,” show potential dunes (upper right) on 2014, it revealed dunes on the neck and Claudin says. That means the thousands of the surface of Jupiter’s volcanic moon both lobes, raising the question of how an known comets — and billions of estimated Io. The dark material in the lower left of object with little to no atmosphere could ones — may all create dunes of their own this image is recently cooled lava, while have windblown features. when they draw near the Sun. Future the brighter white may be deposits of spacecraft may be better prepared to probe material from frost vaporized by the The answer comes from the heart of the any dunes that are forming or frozen on lava as it flowed. NASA/JPL-CALTECH/RUTGERS comet. As the comet draws near the Sun, the surface. icy material from its nucleus begins to con- FIRE AND ICE vert to gas, working its way to the surface. But like a cometary atmosphere, some Along the way, it carries bits of dirt, which consider the evidence tenuous. “I’ve never A recent paper published April 19 are released as the ice sublimates and cre- been convinced,” Horst says. She states in Nature Communications has ates an extremely thin envelope around the that a common problem in planetary sci- combined 14-year-old imagery nucleus, called the coma. Winds generated ence is the association between a feature from NASA’s Galileo mission with by the change in temperature as the comet seen on another world and the terrestrial models of how grains move to rotates are strong enough to move the dirt. counterpart it resembles. “Just because explain how dunes might form on Gravity is weak on the tiny comet, making something looks like a process we’re famil- the solar system’s most volcanic it easier to keep large particles aloft. Thus, iar with doesn’t mean it is a process we’re world: Jupiter’s moon Io. The study material from within the nucleus is ulti- familiar with,” she says. After all, humans shows how on this moon, grains mately smeared across the ground to like to identify and categorize what we see, of rock or frost are not carried by form dunes “almost automatically,” says but sometimes what we perceive as a par- winds, which are weak in the thin Claudin, one of the authors of the research ticular feature — say, a dune — could turn atmosphere. Instead, as hot lava reporting these dunes. out to be nothing. Think of the pyramid mixes with sulfur dioxide (SO2) and face that have been identified on Mars frost underground, the SO2 turns Such dunes can only form when the — when examined closely or from another to gas that vents through the sur- comet is near the Sun. Over its 6.4-year angle, they’re just rocks. face. This outgassing is “dense orbit, Churyumov-Gerasimenko spends and fast moving enough to move most of its time in the cooler regions of Nonetheless, in a 2017 paper published grains on Io and possibly enable the solar system, near Jupiter, its surface in Aeolian Research discussing how our the formation of large-scale fea- unchanging. Claudin estimates that the understanding of dune formation has tures like dunes,” according to comet only actively forms new dunes for changed as solar system worlds are studied first author George McDonald about two weeks every orbit. in greater depth, Diniega, Radebaugh, of Rutgers University in a press Silvestro, Tefler, and others argue that release. But there’s nothing particularly unique recognizing dunes is the first step in identi- fying them. By setting up a flexible policy And indeed, Galileo did spot When it arrived at Comet 67P/Churyumov- for identifying windblown features, the dunelike features on the moon. Gerasimenko, the Rosetta spacecraft sent back researchers hope to make formerly vague The researchers closely examined up-close images of the surface that showed features classifications more consistent. Ideally, the the features’ dimensions and the scientists had never expected to see on a comet — identification of dunes on worlds such as spacing between crests, conclud- including possible dunes. ESA/ROSETTA/MPS FOR OSIRIS TEAM Venus and Pluto would follow a similar ing these formations do look like path to those on Mars. Once a mission dunes seen elsewhere in the solar MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA observes suspected dunes, the next genera- system, including Earth. “Our stud- tion of spacecraft can perform more ies point to the possibility of Io as detailed observations to study their charac- a new ‘dune world,’ ” McDonald teristics and analyze patterns of individual said. “This work tells us that the candidates to confirm or deny their status environments in which dunes are as dunes. Subsequent missions can then found are considerably more classify the landscape even further. varied than the classical, endless desert landscapes on parts of And as observations of other worlds Earth.” — Alison Klesman (including comets) continue, scientists hope to get a better feel for what is possible WWW.ASTRONOMY.COM 27 elsewhere, allowing them to refine their models of how dunes form and move, on Earth and beyond. Nola Taylor Tillman is a freelance writer with a passion for astronomy, planetary science, and space missions.

This month is a great opportunity to see Jupiter at its best. BY MICHAEL E. BAKICH •

n 2022, Jupiter reaches opposition — the point in its orbit make its equatorial diameter 5,800 miles opposite the Sun as seen from Earth — on Sept. 26. It’s (9,300 kilometers) greater than its polar also the giant planet’s closest approach to Earth since diameter. October 1963. On the 26th, Jupiter will blaze at magnitude Rather than taking a quick look every I–2.9, making it the brightest starlike object until Venus now and then, try observing Jupiter over rises shortly before sunrise. a series of nights. In addition to the If you can’t observe Jupiter exactly at stars flanking Jupiter and can form some changing positions of its moons, the opposition because of a personal com- unusual arrangements. planet’s period of nine hours and 55½ mitment or clouds, don’t fret. You’ll have minutes brings all of its visible area into plenty of time to see the king of the plan- When you turn your gaze back to the view during a single night. Long-term ets while it’s big and bright: At no time planet, insert an eyepiece that provides a observations may reveal individual fea- from July 20 through Dec. 3 does its magnification around 100x, and the first tures becoming more or less prominent magnitude dip below –2.6. details you’ll notice will be a pair of dark and even disappearing for long stretches stripes oriented parallel to the planet’s of time. On its opposition date, Jupiter sports equator. These stripes — one above and an apparent diameter of 49.9\", which is one below Jupiter’s equator — are the Spot the Spot quite close to its greatest possible size of North and South Equatorial Belts. 50.1\". And between the two dates above, Through larger telescopes and with Jupiter’s most famous atmospheric its apparent size is at least 43\". So, now is higher magnifications, more belts and feature is the Great Red Spot (GRS), a the time to set up your telescope, crank zones come into view. Planetary observ- high-pressure storm that lies 22° south up the power, and observe Jupiter and ers call the light-colored bands zones and of Jupiter’s equator, drifting slowly its moons in all their glory. the darker ones belts. through the South Equatorial Belt. You’ll spot other similar features, but Moving right along At magnifications above 250x, Jupiter most are white and none are as large. appears squished, bulging at its sides. The GRS has a north-south width of Jupiter first entered Pisces in mid- That’s not an illusion. The planet’s rapid 8,700 miles (14,000 km) and a vari- April; then, from late June until early rotation and the fact that it is not solid able east-west width that was measured September, it crossed in front of some at some 25,000 miles (40,000 km) stars in the northwestern corner of the Conjunction in the 1890s. The storm is slowly constellation Cetus the Whale before returning to Pisces. This whole region Sun Moon eclipsed lacks any bright stars, so it will provide Moon occulted a huge contrast to Jupiter’s brilliance. Earth In fact, the nearest 1st-magnitude star, Jupiter Fomalhaut (Alpha [α] Piscis Austrini), Opposition Shadow transits lies nearly 35° away. ABOVE: Opposition occurs when a planet that Moon transiting For amateur astronomers in mid- orbits outside of Earth’s orbit is positioned northern latitudes, the planet’s location directly opposite the Sun. Around opposition Not to Line of sight in Pisces means it will climb around is when a planet will be closest to Earth — scale from Earth halfway up the sky — not terrible, but prime time to observe it. ASTRONOMY: ROEN KELLY still some distance from where you’d get Earth the best views. For anyone at latitude 40° RIGHT: In this diagram, Jupiter has not yet north on the date of opposition, Jupiter’s reached opposition, and the planet’s shadow Sunlight altitude at local midnight will be 50° extends off to the west (right) as seen from above the southern horizon. In the Earth. Observers would be able to see the Northern Hemisphere, for each degree outer moon be eclipsed, emerge from eclipse, of latitude south of 40° north an observer and then be occulted. However, the inner is, Jupiter will appear 1° higher; for each moon will be occulted before it emerges from degree north of 40°, it will be 1° lower. eclipse. A moon and its shadow can transit the planet, though not necessarily at the Crank up the power same time. ASTRONOMY: ROEN KELLY Through a telescope, Jupiter shows more detail than any other celestial object except the Moon. Even a 2-inch scope will show the planet’s four larg- est moons. The moons look like bright WWW.ASTRONOMY.COM 29

PISCES Sadalmelik Jupiter reaches opposition Sept. 26 but will Jupiter A Q UA R I U S dominate its region of the sky for months. It spends Neptune the last half of 2022 in Pisces and Cetus, an area devoid of bright stars. ASTRONOMY: ROEN KELLY CETUS Saturn Diphda shrinking, however, and is currently just Skat 10,000 miles (26,000 km) across. Deneb Algedi It also changes color because clouds at higher levels and of different composi- CAPRICORNUS tions condense above it. The GRS has varied from brick red during the 1960s Fomalhaut PISCIS to pale pink in the 1990s. Since 2000, the AUSTRINUS spot’s hue has remained light orange. SCULPTOR Moving moons 10° Jupiter’s four largest moons are known as the Galilean satellites, named for their Sept. 26, 11 P.M. discoverer, Italian astronomer Galileo Looking south Galilei. On Jan. 7, 1610, Galileo saw three stars in a straight line, two on one side JOVIAN FUN FACTS of Jupiter and one on the other. The next night, their positions had changed. Five • Jupiter’s magnetosphere is the largest structure in the solar system. If it were visible nights later, he spotted a fourth star. from Earth, it would appear larger than the Full Moon. Galileo concluded that the “stars” were actually bodies revolving around • On a moonless night at a dark site, Jupiter can cast a visible shadow. Jupiter like the Moon circles Earth. His • At its equator, Jupiter rotates at 28,100 mph (45,300 km/h), more than 27 times as fast discovery made Io, Europa, Ganymede, and Callisto the first objects in the solar as Earth. system to be observed despite being invisible to the naked eye. • If Jupiter were hollow, it could hold 1,320 Earths. • On average, Jupiter travels 5' per day against the background stars. So, in a little over The shadow of Ganymede falls across Jupiter in this image taken by NASA’s Juno probe. The shadow six days, the giant planet moves roughly the width of the Full Moon. seems especially large in this image because of how close to the planet Juno was — just 44,000 • The King of Planets is almost 318 times as massive as Earth. miles (71,000 km), or one-fifteenth the orbital • Jupiter reflects 34 percent of the sunlight that falls on it. distance of Ganymede. Swirling storm systems • The brightest planetary satellite visible from Earth (not counting the Moon) is Ganymede. in the planet’s belts and zones are also visible. At opposition, the solar system’s largest moon glows at magnitude 4.4, a brightness that IMAGE DATA: NASA/JPL-CALTECH/SWRI/MSSS. IMAGE PROCESSING BY THOMAS would make it visible to the naked eye if the glare from Jupiter didn’t overwhelm it. THOMOPOULOS © CC BY

The ever-changing configuration of Jupiter’s Great Red Spot races through this set of near its poles. Through bigger scopes, these moons can lead to four different images, taken at intervals of roughly one hour. Due you might be able to see each satellite’s types of observational events. to Jupiter’s rapid rotation, you can observe the (extremely) subtle color. entire planet in one night. CHRISTOPHER GO An eclipse occurs when a satellite Less light, better view moves through Jupiter’s shadow, but is reversed: The satellite begins its transit not positioned behind the planet from and the shadow follows. The best advice I have for Jupiter observ- our point of view. ers is to use color filters to bring out Please note that any of these events details you won’t see otherwise. And An occultation happens when a satel- can occur simultaneously among the although they’re called “color” filters, lite passes behind Jupiter. These events four moons. For example, you might they produce non-color (grayscale) views. occur along the planet’s limb (edge). observe one or more satellites in transit Their purpose is to enhance the contrast Eclipse events are easier to observe than across Jupiter, concurrent shadow tran- between features that are next to one occultations because eclipses usually sits, or multiple moons occulted by the another. Astronomical filters screw into take place some distance from Jupiter’s planet. the bottoms of eyepieces, which have limb. Moons always disappear into matching threads. Like eyepieces, they occultation at the west side of Jupiter If you have a 10-inch or larger scope come in two sizes, 1¼\" and 2\". and reappear at the planet’s east side. and a night with great sky conditions, look for details on the moons. With Manufacturers label filters by color A transit occurs when a moon moves high magnification (above 350x), you’ll and number. For better views of Jupiter’s in front of the planet. A transiting satel- resolve their disks, especially during dark reddish-brown belts than you’d nor- lite always moves from east to west transits when the moons’ glare drops mally get, use a green (No. 58) or blue across Jupiter’s face. The satellites them- (No. 38A) filter. Blue also works best to selves look like bright dots against because Jupiter’s lit background sharpen any bright cloud features. A yel- Jupiter’s dark belts. When a satellite lies provides less of a contrast than low (No. 12) filter will darken the planet’s in front of the brighter zones, however, the black sky. Zoom in on bluish features such as festoons, small it’s hard to see unless you follow it from Ganymede, the largest moon, regions that appear from time to time the time the transit starts. first. Look for light-colored ice near the planet’s equator. A shadow transit happens when a Most observers use red (No. 23 or moon’s shadow moves across Jupiter’s No. 25A) filters to enhance white spots disk. Shadows of the moons look like and ovals in the South Temperate Belt small black dots on Jupiter through any and South Temperate Zone. Red filters telescope. Transiting shadows also move also seem to work well on boosting the from east to west across Jupiter. contrast of the northern and southern borders of the major belts. Before opposition, from our perspec- tive on Earth, Jupiter’s shadow extends Remember, filters don’t make features west of the planet, so a satellite will be brighter. Quite the opposite. So, when eclipsed before it’s occulted. The satellite you use them you’ll get better results being eclipsed gradually fades as it enters through larger telescopes with eyepieces Jupiter’s shadow, which is pretty cool to that provide medium to high magnifica- watch. tions. If you have a 6-inch or smaller tele- scope, use lighter filters. For example, use The two outer satellites, Ganymede light red (No. 23A), light yellow (No. 8), and Callisto, are usually far enough from or light blue (No. 82A) filters rather than Jupiter to reappear from an eclipse, so their darker counterparts. you’ll be able to see them disappear into occultation. However, Io and Europa An audience with the king emerge from their eclipses after their occultations start, so you won’t see them As summer transforms to fall in the reappear — they’ll be behind the planet. Northern Hemisphere, Jupiter provides a brilliant target for any observer, no mat- After opposition, when Jupiter’s ter your equipment. It’s so bright, in fact, shadow falls east of the planet, occulta- that you won’t need to head to a dark site tions occur before eclipses. Then, you’ll to view it. Set your scope up in your yard, be able to see Io and Europa disappear pull up a chair, and carve out some time into occultation and reappear from to see the giant planet at its best. eclipse. Michael E. Bakich is a contributing editor For transits and shadow of Astronomy who has observed lots (and transits before opposition, the lots) of Jupiter oppositions. satellite’s shadow falls on the planet before the transit starts. After opposition, this order is WWW.ASTRONOMY.COM 31

SKY THIS MONTH Visible to the naked eye Visible with binoculars THE SOLAR SYSTEM’S CHANGING LANDSCAPE AS IT APPEARS IN EARTH’S SKY. Visible with a telescope BY MARTIN RATCLIFFE AND ALISTER LING Mars observing season is heating up as the Red Planet approaches opposition in two months. Now is the time to perfect your observing technique. ALAN DYER locations from night to night. Iapetus moves from an Oct. 4 inferior conjunction to reach western elongation Oct. 24, the day after Saturn reaches a sta- tionary point on its retrograde loop. The evening of Oct. 3 in the U.S., you can spot this 11th-magnitude moon a mere 18\" southeast of the planet. By late October, Iapetus’ brighter hemisphere is facing us, increas- ing its magnitude to 10. You’ll find it 8' due west of Saturn, OCTOBER 2022 with a trio of stars of similar magnitude to the moon’s north. You can easily find Neptune The planets get busy by using Jupiter as a guide. The ice giant starts the month about 9.5° west-southwest of the brighter planet. Neptune is a month past opposition and well placed nearly all night in eastern Mars, Jupiter, and 5. You’ll find Saturn a pleasant mornings of Oct. 8 and 24, and Aquarius, a few degrees south of Saturn are October’s 30° high in the southern sky due south Oct. 16. Fainter the Circlet of Pisces. Binoculars major attractions. They offer during the first few hours of Tethys, Dione, and Rhea, all will reveal it about 5.5° south of stunning views at various times darkness. magnitude 10, change relative Lambda (λ) Piscium. A bright of night. In addition, Uranus Saturn is elegant when and Mercury are occulted by viewed through a telescope at Distant giants the Moon, though both events low magnification — set in a are challenging observations. wealth of black sky, it resolves The month wraps up with a into a beautiful disk surrounded PEGASUS Enif partial solar eclipse visible by its ring system. No one ever Alpheratz across Europe and the Middle forgets their first view of this Markab East, while worldwide, the magnificent planet. The disk Saturn Orionid meteor shower occurs spans 18\", with its polar diam- CAPRICORNUS in good conditions. eter a smaller 16\". As Earth pulls away from Saturn after August’s A Q UA R I U S Swing your telescope to east- opposition, the disk shrinks by Deneb Algedi ern Capricornus for a fine view about 3 percent this month. of Saturn each evening this PISCES Neptune Jupiter Moon PISCIS AUSTRINUS month. It’s visible at nightfall The rings span 40\" across Fomalhaut and doesn’t set until nearly their long axis, an overwhelm- 3 A.M. in early October, and ing sight. Their apparent tilt to 10° shortly before 1 A.M. at the end our line of sight is 15°, with of the month. The ringed planet their northern face sunlit. Oct. 7, 1 hour after sunset Looking east glows at magnitude 0.5, making Titan, Saturn’s largest moon, it the brightest feature of shines at magnitude 8.5 — an Jupiter, Saturn, and Neptune (visible in binoculars) dominate the evening sky Capricornus except when the easy target for small telescopes. in October. On the 7th, the Moon stands due south of the solar system’s most Moon is around on Oct. 4 and You’ll find it north of Saturn the distant planet. ALL ILLUSTRATIONS: ASTRONOMY: ROEN KELLY 32 ASTRONOMY • OCTOBER 2022

RISING MOON I Look again THAT YOU CAN EXPERIENCE the pleasure Aristoteles, Protagoras, and Vallis Alpes of the unexpected when you see it under a new light is an idea that applies nicely to OBSERVING lunar observing. Craters, scarps, and valleys Protagoras Aristoteles HIGHLIGHT take on a new face under a sunset illumina- tion, compared with their traditional appear- THE MOON occults two ance when the Moon is waxing toward Full. planets this month: first Later in the evening of the Oct. 14 (around 11 P.M.), a waning gibbous Luna is URANUS on Oct. 11/12, then oddly unfamiliar. First to catch the eye along MERCURY on Oct. 24. the terminator is the snaking Serpentine Ridge, its relationship to the entire Sea of Vallis Alpes N Serenity now easy to see. Jump halfway to the pole to the large gibbous Moon lies 3° south of and detailed crater Aristoteles. The low E Neptune late on Oct. 7. Neptune Sun angle transforms its apron of impact glows at magnitude 7.7; a tele- splatter into an expanse of roughness Familiar lunar features can appear scope reveals its dim bluish disk, whose texture is as fine as the night and new and strange in the reversed your telescope allow. The north-south lighting of Last Quarter. CONSOLIDATED LUNAR ATLAS/UA/LPL. INSET: NASA/GSFC/ASU spanning 2\". shadow line down its middle sports a large familiar lighting conditions on the evenings of the Jupiter is the brightest object scoop. Trace this light back to the small cra- 1st and 31st, you might never suspect the unusual ter breaching the western flank that lets the is hiding in plain sight. in the evening sky aside from Sun shine through. the Moon. It is visible all eve- The shadows intensify on the 16th, with the ning, shining at magnitude –2.9. Farther north and west, Protagoras lies Sun dropping down in the lunar sky. Nearby, the It stands in southern Pisces, sunken in the basin of Mare Frigoris, almost Alpine Valley (Vallis Alpes) cutting diagonally below the Square of Pegasus. resembling the hole in a golf green. Typical through rough terrain is a sight always worth the craters in the region have raised rims and time. If the atmosphere is steady, pump up the After opposition in late western-facing flanks brightly lit by the power and look for the rille running down its mid- September, Jupiter maintains an setting Sun. But here, the ancient lava dle. The valley rim will still be illuminated on the apparent diameter of 50\" for a flow came right up to the western lip of 17th for a post-midnight view. few days into October, dimin- Protagoras. Under a waxing crescent’s ishing slightly to 48\" by the end of the month. Early evening views are nice, and things only improve as Jupiter moves above METEOR WATCH I A good show 45° altitude around 11 P.M. local time in early October; this occurs progressively earlier Orionid meteor shower THE ORIONID METEOR SHOWER as the month flows on. is active from Oct. 2 through Nov. 7, Jupiter’s dynamic atmo- GEMINI Mars Pleiades with the peak occurring the morning sphere is its main attraction. of Oct. 21. The radiant in northeastern Brownish belts straddle the Radiant TAU R U S Orion rises by 10:30 P.M. local time. A equator and carry additional waning crescent Moon rises around spots and festoons across the Procyon Betelgeuse Aldebaran 3 A.M. local time and is not a limiting central median in minutes. CANIS factor this year. The shower has a Watch for the Great Red Spot’s MINOR ORION consistent zenithal hourly rate of up to 20 meteors per hour at maximum, Rigel corresponding to an observable rate of 15 to 18 meteors per hour between occasional appearance. Be Sirius 2 A.M. and dawn. Rates increase as patient and wait for fleeting ERIDANUS morning hours progress. moments of atmospheric CANIS MAJOR The Orionids are a product of historic passes of Comet 1P/Halley stillness that offer the most through the inner solar system. Grab a hot chocolate, wrap up warmly, incredible views of the gas giant. and settle onto a lounger to watch the winter constellations rise and The four Galilean moons 10° wait for the glowing embers of — Io, Europa, Ganymede, Halley’s dusty debris to momentarily brighten the sky. and Callisto — orbit with ORIONID METEORS Oct. 21, 5 A.M. periods of two to 16 days. Looking south Past opposition, the moons Active dates: Oct. 2–Nov. 7 transit ahead of their shad- Peak: Oct. 21 The Orionids’ radiant rises late in the ows. A series of Europa Moon at peak: Waning crescent evening and is well-placed for early Maximum rate at peak: morning viewing before dawn. — Continued on page 38 20 meteors/hour WWW.ASTRONOMY.COM 33

STAR DOME N LYNX ` M82 HOW TO USE THIS MAP J O R M81 _ This map portrays the sky as seen k near 35° north latitude. Located inside the border are the cardinal ¡ DALIS M A ` directions and their intermediate d points. To find stars, hold the map _ O L E C overhead and orient it so one of AURIGA Capella the labels matches the direction c R PA you’re facing. The stars above the map’s horizon now match NE _ what’s in the sky. M I N O R NCP c The all-sky map shows URSA how the sky looks at: Polaris a ` 10 P.M. October 1 _ 9 P.M. October 15 8 P.M. October 31 ¡ b Planets are shown _ NGNCG8C69884 ` at midmonth a a c Algol PERSEUS a CEPHEUS b Pdleiades ¡ b ` l TAU R U S ANDROMEDA IA f` + _ a` _ P O I ERTA _ d M33 CASS ` T E C c LA ` b R I A A a _ Deneb Path N M31 _ P E G A S U S b d CYGNUS Uranus G R U_L of IES _ `a U kd the Sun `+ MAP SYMBOLS M Open cluster b Globular cluster Diffuse nebula E (ecliptic) ¡ r Planetary nebula Galaxy _ PISCES a d c a M27 _ k _ M15 ` U S Mira c _ Enif DE H I N Altair ¡ L P STAR CETUS Jupiter a e EQUULEUS MAGNITUDES _ AQUARIUS e Sirius 0.0 3.0 d ` 1.0 4.0 2.0 5.0 o STAR COLORS _ A star’s color depends ` b ba ` on its surface temperature. Saturn The hottest stars shine blue SE SGP NGC 253 SCULPTOR _ CAPRICORNUS •• Slightly cooler stars appear white _ Fomalhaut MICROSCOPIUM • Intermediate stars (like the Sun) glow yellow APUI SSCTIRSI N U S a • Lower-temperature stars appear orange _ • The coolest stars glow red ` GRUS • Fainter stars can’t excite our eyes’ color _ receptors, so they appear white unless you use optical aid to gather more light S BEGINNERS: WATCH A VIDEO ABOUT HOW TO READ A STAR CHART AT www.Astronomy.com/starchart.

a OCTOBER 2022 SUN. MON. TUES. WED. THURS. FRI. SAT. _ c d 1 Mizar M51 2345678 URSA M 9 10 11 12 13 14 15 ¡ 16 17 18 19 20 21 22 b CBOORROENAAL I S ¡ NW d f b BOÖTES a DRACO ` ` _ 23 24 25 26 27 28 29 ILLUSTRATIONS BY ASTRONOMY: ROEN KELLY i S 30 31 E Note: Moon phases in the calendar vary in size due to the distance from Earth and are shown at 0h Universal Time. /d M13 L a U C c ER H ` ¡ Vega ` SERPENS CAPUT V U L P E C U L A M57 _LY R A + b _ a SAGITTA _ ` a _ ¡ W CALENDAR OF EVENTS _ b_ OPHIUCHUS g 1 Mercury is stationary, 11 A.M. EDT AQUILA c CSAEURDP EAN S ` 2 First Quarter Moon occurs at 8:14 P.M. EDT 4 The Moon is at perigee (229,488 miles from Earth), 12:34 P.M. EDT ` d c 5 The Moon passes 4° south of Saturn, noon EDT b 7 Asteroid Vesta is stationary, 2 A.M. EDT d The Moon passes 3° south of Neptune, 11 P.M. EDT 8 The Moon passes 2° south of Jupiter, 2 P.M. EDT h _ M11 Pluto is stationary, 2 P.M. EDT M16 Mercury is at greatest western elongation (18°), 5 P.M. EDT SCUTUM i SW e 9 Full Moon occurs at 4:55 P.M. EDT 12 The Moon passes 0.8° north of Uranus, 3 A.M. EDT M17 d 15 The Moon passes 4° north of Mars, 1 A.M. EDT M20 17 The Moon is at apogee (251,238 miles from Earth), 6:20 A.M. EDT / j M22 + Last Quarter Moon occurs at 1:15 P.M. EDT m h M8 18 Asteroid Juno is stationary, 8 P.M. EDT o  b 21 Orionid meteor shower peaks c a 22 Venus is in superior conjunction, 5 P.M. EDT 23 Saturn is stationary, 5 A.M. EDT A RI US 25 New Moon occurs at 6:49 A.M. EDT; partial solar eclipse 29 The Moon is at perigee (228,845 miles from Earth), 10:36 A.M. EDT S A G I TT _ SOTNRAA ¡ d 30 Mars is stationary, 7 A.M. EDT ` _ OR L IS AU C ` WWW.ASTRONOMY.COM 35

PATHS OF THE PLANETS AUR Bamberga CNC GEM Mars TRI ORI ARI CMi Mercury appears LEO (ecliptic) MON PEG bright before dawn Pallas PSC BOÖ Ceres the Sun Uranus in early October Path of Euterpe TAU VIR SEX Celestial equator Jupiter VenusSun H YA ERI Neptune Juno CRT CET CRV LEP Vesta SCL FOR PYX PsA ANT PUP COL CAE VEL PHE CEN GRU Moon phases Dawn Midnight 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 To locate the Moon in the sky, draw a line from the phase shown for the day straight up to the curved blue line. Uranus THE PLANETS Jupiter THE PLANETS IN THE SKY IN THEIR ORBITS Neptune These illustrations show the size, phase, Arrows show the inner and orientation of each planet and the two Saturn brightest dwarf planets at 0h UT for the dates planets’ monthly motions in the data table at bottom. South is at the top to match the view through a telescope. and dots depict the outer planets’ positions at midmonth from high above their orbits. Venus Mars Pluto Mercury Ceres Mercury Greatest western elongation is October 8 Ceres Mars Jupiter PLANETS MERCURY VENUS Earth Venus Date Oct. 15 Oct. 15 Superior conjunction Magnitude –0.9 –3.9 Angular size 6.0\" 9.7\" is October 22 Illumination 76% 100% Distance (AU) from Earth 1.129 1.717 Distance (AU) from Sun 0.327 0.721 Right ascension (2000.0) Declination (2000.0) 12h22.3m 13h13.0m –0°15' –6°24' 36 ASTRONOMY • OCTOBER 202 2

This map unfolds the entire night sky from sunset (at right) until sunrise (at left). Arrows OCTOBER 2022 JULYand colored dots show motions and locations of solar system objects during the month. 1 CYG LYR HER BOÖ Callisto 2 CrB COM VUL Europa 3 Jupiter DEL Io 4 Callisto 5 SGE EQU AQL OPH A partial solar eclipse VIR Io AQR occurs October 25 Europa across portions of 6 Ganymede 7 Europe, Asia, and Africa CAP SCT Ganymede Saturn LIB Sun CRV Pluto Path of the Moon JUPITER’S 8 SGR MOONS 9 10 MIC Dots display 11 positions of 12 CrA SCO Galilean satellites 13 TEL at 11 P.M. EDT on the date shown. LUP CEN South is at the top to match the Early evening view through a telescope. 65 43 21 31 30 29 28 27 26 25 24 14 15 Jupiter 16 17 Saturn S 18 WE 19 N 10\" 20 21 Uranus Neptune Pluto 22 23 MARS CERES JUPITER SATURN URANUS NEPTUNE PLUTO 24 25 Oct. 15 Oct. 15 Oct. 15 Oct. 15 Oct. 15 Oct. 15 Oct. 15 26 –0.9 8.8 –2.9 0.5 5.7 7.7 15.2 27 13.3\" 0.4\" 49.2\" 17.8\" 3.8\" 2.4\" 0.1\" 28 90% 98% 100% 100% 100% 29 0.705 3.153 4.006 9.362 100% 100% 30 1.464 4.954 18.782 29.033 34.533 31 2.554 9.855 19.681 29.914 34.625 5h32.4m 10h43.7m 0h06.4m 21h24.7m 3h01.0m 23h36.1m 19h53.0m 23°06' –1°03' –16°35' 16°43' –3°55' –23°09' 16°05'

WHEN TO SKY THIS MONTH — Continued from page 33 VIEW THE Busy system Others will see a near miss, PLANETS with Uranus south of the Moon. EVENING SKY Callisto S It’s challenging to see magni- Jupiter (east) Jupiter tude 5.7 Uranus reappear near Saturn (south) such a bright Moon, but there’ll Neptune (east) W Io Europa be lots of interest. The timing MIDNIGHT Oct. 16, 12:15 A.M. EDT Europa’s shadow of the event is heavily location- Mars (east) Jupiter (south) dependent but occurs around Saturn (southwest) Uranus (east) 11:45 P.M. (For example, resi- Neptune (south) Ganymede 30\" dents of Denver see Uranus appear at about 11:52 P.M. MDT Catch Europa and its shadow transiting before Io disappears behind Jupiter on the 11th). Observers in the MORNING SKY early on Oct. 16 (late on Oct. 15 west of the Eastern time zone). Ganymede, eastern U.S. will see a similar Mercury (east) dimmed by Jupiter’s shadow, reappears just before 1 A.M. EDT. event on the first day of 2023. Mars (southwest) Uranus is approaching next Uranus (west) transits followed by Io occulta- The next planet along the month’s opposition. To find it, tions occur Oct. 8, 15/16, and ecliptic, Uranus, is occulted by locate magnitude 2.5 Menkar 22/23. Each of these is followed the Moon Oct. 11/12. Uranus in Cetus. Uranus stands about located between Sigma (σ) and by an Io transit on the evenings currently lies in the sparse 12° due north of the star, 53 Arietis all month. of Oct. 9, 16, and 23. regions of southeastern Aries. slightly less than two field Through a telescope, try to On Oct. 8, Europa’s transit Those in the northwestern diameters in 7x50 binoculars. discern the 4\"-wide disk. At begins at 8:49 P.M., its shadow U.S. will see the occultation. The aqua-colored planet is more than 1.7 billion miles begins to transit at 9:25 P.M., from Earth, it’s a marvelous and Io disappears at 10:42 P.M. 15\" Mars grows from 12\" to 15\" this month. sight. Use higher magnifica- (all times EDT). On Oct. 15/16, By December’s opposition, it will span 17\". tions on nights of good seeing events occur in the same order for the best views. at 11:03 P.M., 12:01 A.M., and 12:26 A.M. (the last two events are on the 16th for those in the COMET SEARCH I The understudy takes over Eastern time zone only). On Oct. 23, events are in a slightly different order: Europa transits “SEE YA NEXT YEAR!” is Comet C/2017 K2 (PanSTARRS) starting at 1:18 A.M., Io disap- the thing to say to C/2017 K2 pears at 2:11 A.M., and Europa’s (PanSTARRS) as darkness falls on N Oct. 1 shadow slips onto the disk at the first few nights of October, 2:36 A.M. (Some or all events before the waxing Moon’s light 3j r occur late on the 22nd in west- obscures it. You’ll need a tree- ern time zones.) Also on the less southwestern horizon good LUPUS 5 22nd, Ganymede is occulted by enough to also see the False Path of Jupiter at 11:30 P.M. EDT. Comet asterism, spearheaded E by NGC 6231 in the Scorpion’s Comet PanSTARRS Io and its shadow transit the 7 day after each of the Europa events. These transits (moon, back. Thanks to Earth’s curvature, shadow) occur at 7:53 P.M. and 8:14 P.M. on the 9th, 9:38 P.M. PanSTARRS gains a few degrees of and 10:09 P.M. on the 16th, and 11:24 P.M. (Oct. 23) and 12:05 altitude for observers in the lower A.M. (Oct. 24 for East Coast observers only; all times are 48 states. again EDT). Note how the time between each moon and PanSTARRS should be sharpest e shadow transit stretches as to the south, with its soft, white October progresses — a feature 0.5° of Earth’s changing view of the dust tail fanning out to the east and north. Amazingly, the comet Comet PanSTARRS is readily visible in the Northern Hemisphere only during is still beyond the orbit of Mars early October. Visit our website to find observing charts for C/2022 E3 (ZTF) and a couple of months before later in the month. perihelion. Folks south of the equator now get a full year of it tickling naked-eye visibility. Gravity then loops the dirty snowball back north, treating us to a passage through Orion in December 2023. Fresh on the celestial stage, C/2022 E3 (ZTF) was discovered in March and is set to peak brighter than Jupiter system relative to the 6th magnitude in early 2023. For now, use an 8-inch scope under dark evening skies to pick out the direction of sunlight. 11th-magnitude puffball in Corona Borealis at the end of the month. 38 ASTRONOMY • OCTOBER 2022

LOCATING ASTEROIDS I Venerable Vesta Pulling up close THIS IS A WONDERFUL TIME to spot your first (or hundredth) asteroid. From a suburban backyard or balcony, just point your Oct. 24, 30 minutes before sunrise binoculars one to two fields to the lower left of Saturn and tag the second-brightest dot. Looking east LEO Modestly well-placed in the southeastern sky mid-evening, BOÖTES VIRGO 4 Vesta parades as a 7th-magnitude star. Use the parallelogram Arcturus at the east end of Capricornus, anchored by magnitude 2.8 Moon Delta (δ) Capricorni, to orient yourself. Then drop one field to the Mercury lower left. Make a sketch of the four brightest dots and return every few nights to pick out the one that moved. Globular cluster M30 is one field to the right — check it out if you’re on the south side of town. It looks a bit fuzzy, just right of a magnitude 5.2 star. The fourth main-belt asteroid to be discovered, Vesta spans 10° more than 320 miles across and was intently examined by the Dawn spacecraft a decade ago. Heinrich Olbers spotted it in 1807 and might be amazed to know that astronomers have deduced that its oval body has a core, mantle, and crust. The Moon and Mercury sit roughly 1° apart just before sunrise on Oct. 24. Easy pickings Later that morning, some will see the Moon occult Mercury. Mars is a stunning object in midnight, the following features b a the middle of Taurus on Oct. 1. face Earth (for Midwestern N It’s now only two months from observers): Oct. 1: Olympus opposition as we enter the best Mons; Oct. 5: Tharsis Ridge and g time to observe the Red Planet. Valles Marineris; Oct. 14: Solis Mars rises around 10 P.M. and Lacus; Oct. 22: Syrtis Major and E¡ brightens from magnitude –0.6 the Hellas basin; Oct. 30: Mare to –1.1 during the month. It Sirenum. Enjoy becoming A Q UA R I U S CAPRICORNUS forms a stunning triangle with familiar with these features 30 two bright red giant stars: as Mars approaches its early Betelgeuse to its south and December opposition. 25 Aldebaran to its west. 20 Mercury achieves its best The Moon joins Mars late on morning apparition for Path of Vesta 15 Oct. 14, separated by less than Northern Hemisphere 10 4°. The Red Planet also stands observers. It rises in the east 5 1° within 1.1° of the Crab Nebula 68 minutes before the Sun on (M1) for about three days start- Oct. 1 but is only magnitude Oct. 1 M30 ing on this date, passing due 0.9. By Oct. 5, it brightens to north of the nebula on the 17th. magnitude 0. You’ll find it a Seventh-magnitude Vesta is relatively simple to spot this month near The planet’s eastward motion respectable 7° high 45 minutes Delta Capricorni, also called Deneb Algedi. slows to a halt by Oct. 30, when before sunrise. It reaches great- it sits 2.7° north of Zeta (ζ) est elongation (18°) on the 8th, in bright twilight — a challenge Europe, northeastern Africa, Tauri. It then begins a retro- now at magnitude –0.4. requiring very clear skies and a southwestern Asia, the Middle grade path. Mercury reaches magnitude –1 level eastern horizon. During East, India, and portions of by Oct. 16, but two days later daylight hours, the Moon Russia. Observers in London Mars transits the local has fallen in altitude to 5° high occults Mercury soon after experience the eclipse from meridian around 5 A.M. This is 45 minutes before sunrise. 10 A.M. EDT for U.S. observers. 10:08 A.M. to 11:51 A.M. local the best time to view the planet This is a challenging event time, with a maximum obscu- or record high-speed video, and The planet continues to drop because it is near the Sun (only ration of 15 percent (26 percent perfect your observing tech- lower each morning. Can you 10° away). Significant safety of the Sun’s diameter). Others niques. Its apparent diameter spot Mercury Oct. 24, just over precautions must be undertaken across Europe experience a grows from 12\" to 15\" during 1° southeast of the waning cres- before making any attempts to larger percentage of coverage the month, and its phase grows cent Moon, one day prior to view the occultation — do not and a longer duration. from 88 percent to 94 percent. New Moon? The pair is only 4° randomly scan the sky looking high 30 minutes before sunrise for the Moon. Martin Ratcliffe is a In the hours around local planetarium professional with Venus is out of view, Evans & Sutherland and enjoys GET DAILY UPDATES ON YOUR NIGHT SKY AT reaching superior conjunction observing from Salt Lake City. www.Astronomy.com/skythisweek. Oct. 22. It reappears in the eve- Alister Ling, who lives in ning sky later in the year. Edmonton, Alberta, is a longtime watcher of the skies. A partial solar eclipse occurs Oct. 25, visible across most of WWW.ASTRONOMY.COM 39

4 7 6 5 must-visit astro 2 destinations These museums, With almost two years spent at home, travelers observatories, and telescopes are eager to get a few more miles under their belts. should be on every But before you book your next trip, consider what enthusiast’s travel list. else your destination has to offer, cosmologically speaking. Here are a few space-related destinations BY CAITLYN BUONGIORNO — in alphabetical order — that you should consider checking out the next time you travel. Arcetri Astrophysical Observatory • Florence, Italy Atacama Desert • Chile

3 1 8 9 Arcetri Astrophysical minor bodies of the solar system to perfect for stargazing — so much so that Observatory astrobiology. it is the premier location for professional telescopes. The majority of the European 1Completed in 1872, the Arcetri Looking for more astronomical history Southern Observatory’s (ESO) telescopes in Florence? A half-hour walk from the are situated in the Atacama Desert, Astrophysical Observatory was designed observatory is the final residence of including the Very Large Telescope and to house the largest refractor in Italy: Galileo Galilei. The villa, referred to as the upcoming Extremely Large Telescope. the Amici telescope. With an 11-inch Il Gioiello (The Jewel), is where Galileo This Chilean desert is also home to the objective lens, the telescope retained its served his life sentence (under house Atacama Large Millimeter/submillimeter superlative status for 40 years. arrest) from 1633 until his death in Array, better known as ALMA, the larg- 1642. His tomb, at the Basilica of Santa est radio telescope in the world. German astronomer Wilhelm Tempel Croce, is also just a little over 2 miles used the Amici telescope in his search for (3.5 kilometers) from the observatory. The Cerro Tololo Inter-American new nebulae, and his drawings are still Observatory (CTIO) also resides here. on display at Arcetri. The original Amici 2Atacama Desert CTIO is a complex of around 40 tele- telescope was upgraded twice. It now scopes and instruments, including the houses a 14-inch objective that is The Atacama Desert in Chile is an 4.1-meter Southern Astrophysical currently used for public outreach. astronomer’s paradise. Miles above sea Research (SOAR) Telescope and the Dark level and free from major cities, the des- Energy Survey’s Dark Energy Camera And today, research continues at ert’s arid weather and sparse rain make it (DECam) on the Victor M. Blanco the observatory, as scientists grapple 4-meter Telescope. And while still under with topics ranging from the study of construction at the time of writing, the Vera C. Rubin Observatory (previously named the Large Synoptic Survey Telescope [LSST]) is scheduled to begin full science observations in December of next year. Deutsches Museum • Munich, Germany LEFT TO RIGHT: Both the Amici telescope and the nebulae Wilhelm Tempel drew while using it are on display at the Arcetri Astrophysical Observatory. CELLAI STEFANO/DREAMSTIME Once the Vera C. Rubin Observatory is completed, it promises to compile the largest astronomical catalog of universe. RUBIN OBSERVATORY/NSF/AURA The Deutsches Museum (or the German Museum) is located on a small island in Munich, Germany. MARCO SPROVIERO, BEOBACHTERGRUPPE DEUTSCHES MUSEUM/DEUTSCHES MUSEUM WWW.ASTRONOMY.COM 41

After touring these sites in the day- on floors 3 to 6 (remember that floor 0 is visitors then walk through the history time, make sure you spend your nights scouring the desert skies — the best skies the ground floor in Europe). One floor of the universe with the 360-foot-long in the world — with your own telescope. Observers can spot all the great sights hosts plenty of hands-on physics dem- (110 m) gallery, where one step is equal to the Southern Hemisphere has to offer: the Magellanic Clouds, the Southern onstrations for both kids and a million years. The size of the sphere Cross, Proxima Centauri, and the Carina Nebula, just to name a few! adults so they can better also serves as a handy visual scale Deutsches Museum grasp the basic concepts Be aware when discussing celestial bod- that astrophysicists that some ies, representing either the From our solar system to the explore. The museum observatories Sun or the Milky Way, also has two obser- and telescopes depending on context. 3Big Bang, the Deutsches Museum vatories and a plane- require visitors The Hayden tarium that are open to preregister Planetarium Space Theater in Munich, Germany, gives visitors an for tours. online prior can seat 429 people and uses introductory course on the cosmos. to visits. a scientifically accurate 3D Visitors can explore astronomy topics On top of all that, the museum is home to map of the known universe as BELOW (LEFT TO RIGHT): The Hayden Sphere takes up a majority of the Rose Center for Earth and a wide range of telescopes the foundation of the museum’s Space and houses both the Hayden Big Bang Theater at its base and the Hayden Planetarium and astronomical equipment, Space Shows. Called the Digital Space Theater at the top. Inside, the sphere acts as a visual scale for celestial bodies. D. FINNIN/© AMNH but the must-see attraction is Universe Atlas, this map uses millions of While at the Kennedy Space Center, visitors can Fraunhofer’s Telescope. Astronomer J.G. astronomical observations and is main- walk through the Heroes and Legends exhibit, the Rocket Garden, and even take a tour of the Galle used this 9-inch (23 cm) scope in tained by a team of experts to display a restricted areas of NASA’s space center. As an added bonus, you might even be able to witness 1846 to discover Neptune. hyper realistic view of the universe. a rocket launch — if you time your visit right. 4Rose Center for 5Kennedy Space Center NASA/KIM SHIFLETT Earth and Space Cross two life achievements off Just 55 miles (89 km) outside of Tucson, Arizona, Kitt your bucket list by visiting the Kennedy Peak National Observatory offers both daytime Part of the American Museum of tours and nighttime observing sessions to visitors. Natural History, the Rose Center for Space Center during a rocket launch. The KPNO/NOIRLAB/NSF/AURA/P. MARENFELD OR KPNO/NOIRLAB/NSF/AURA Earth and Space is home to the Hayden Visitor Complex offers the closest pos- Lowell Observatory is home to the 24-inch Clark Refractor, the 13-inch Lawrence Lowell Telescope, Planetarium and a handful of permanent sible public access to a launch, with view- and the telescope that was used to discover Pluto in 1930. CLARKHARUN MEHMEDINOVIC/LOWELL OBSERVATORY exhibits. Appearing to float within a ing locations set up within a few miles glass cube, the top portion of the 87-foot of the launchpads. Countdowns and up- (26 meters) Hayden Sphere houses the to-date information on the next rocket Hayden Planetarium Space Theater. launch are available on their website at In the Hayden Big Bang Theater, visi- www.kennedyspacecenter.com. tors get to watch the birth of the cos- Even if you can’t book a trip mos — narrated by Liam Neeson during a launch (or, worst- — unfolding on a screen below case scenario, the launch their feet. Following a path gets rescheduled), there are spiraling out from the theater, plenty of other things to Rose Center for Earth and Space • New York, New York Kennedy Space Center • Cape Canaveral, Florida 42 ASTRONOMY • OCTOBER 2022

do at the complex, which is divided A few honorable Lowell Observatory into several themed Mission Zones. mentions Visitors can tour the history and future 7Taking advantage of the near-pristine of space exploration by celebrating early Griffith Observatory pioneers and rockets with the Heroes skies Arizona has to offer, Lowell and Legends exhibit, taking a guided Los Angeles, California Observatory also gives visitors a chance bus tour of the restricted areas of to do some solar and nighttime observ- NASA’s space center, and getting a Free to the public, Griffith Observatory ing. But this site is on our list because glimpse at the rockets that launched overlooks Los Angeles atop Mount of the historical telescopes it has on us to the stars. Hollywood in Griffith Park. Offering display. visitors an introduction to astronomy and Kitt Peak National telescopes (despite its light-polluted Lowell Observatory is home to two skies), the observatory also boasts the historic telescopes: The 24-inch Clark 6Observatory best views of the famed Hollywood sign. Refractor and the 13-inch Lawrence Lowell Telescope. Percival Lowell devel- The Kitt Peak Observatory is a beacon National Air and oped his controversial views of intel- of astronomical outreach for astrono- Space Museum ligent martian life while looking mers around the world, even making through the 24-inch Clark Refractor. itself available to virtual visitors during Washington, D.C. The telescope was later used by Vesto peak pandemic times. When open to M. Slipher to determine that distant the public (double check online first), Temporarily closed through fall 2022, the galaxies are moving away from us. Kitt Peak has open hours during the National Air and Space Museum is daytime from 9 a.m. MST to 3:45 p.m. approaching the finish line of a seven-year Visitors can also visit the site where MST, during which you can tour the renovation. By 2025, the museum plans to Clyde Tombaugh discovered Pluto. locations marked for visitors. Keep in have reimagined its 23 exhibits and added Nicknamed the Pluto Discovery Dome, mind that as a working research facility, over 1,400 new objects to its collection. the 13-inch Lawrence Lowell Telescope it does include some buildings that are was used by Tombaugh in 1930 to barred to the public. Royal Observatory discover the ninth planet in our solar system. (Later, in 2006, Pluto was The observatory also offers night- Greenwich, U.K. reclassified as a dwarf planet — a time programs, provided visitors have decision marred by controversy.) registered in advance. Guests can Known as the Home of Time, the Royal choose from three programs that guide Observatory sits on the Prime Meridian The Giovale Open Deck Observatory visitors through observing the night (longitude 0°0’0’’), marking the divide is like a candy shop for telescope enthu- sky. An overnight observing program is between the Western and Eastern hemi- siasts and amateur astronomers. The also available, which places guests in the spheres of the globe. plaza features six advanced telescopes shoes of an astronomer. You will be for observers to look through. The given a dorm room, have dinner in the Teide National Park 24-inch Dyer Telescope is the latest cafeteria with astronomers and staff, addition to the observatory, installed in and be slotted in for telescope time. Canary Islands, Spain 2020. Visitors can purchase a private observing session with the telescope A UNESCO World Heritage site, Teide separately from general admission. National Park has served as a testbed for the European Space Agency’s model rov- ers, thanks to its lunarlike environment. Very Large Array Socorro, New Mexico Closed to the public at the time of writing, the Very Large Array (VLA) in New Mexico is normally open for self-guided tours. This walking circuit culminates with guests standing at the base of one of the 230-ton VLA antennas! Kitt Peak National Observatory • Pima County, Arizona Lowell Observatory • Flagstaff, Arizona WWW.ASTRONOMY.COM 43

Shanghai Planetarium 9South African Dome Theater • Milwaukee, Wisconsin 8The world’s largest astronomy museum, Astronomical With some of the best skies the world Observatory has to offer, the Sutherland site hosts the Shanghai Planetarium is part of the Southern African Large Telescope the Shanghai Science & Technology Founded in 1820, the South African (SALT), the 1.0-meter and 1.9-meter tele- Museum. The planetarium’s overall Astronomical Observatory (SAAO) is scopes, and the Lesedi 1-meter telescope. design is inspired by the orbital motion the national center for optical and infra- (Lesedi means “light” or “enlightenment” of celestial bodies, while the three round- red astronomy. Cape Town hosts the in Sesotho, one of the official languages ed shapes atop the planetarium are meant observatory’s headquarters, while several in South Africa.) Daytime and nighttime to represent the Sun, Moon, and stars. working telescopes are in the Karoo fully guided tours of the Sutherland site region at SAAO’s Sutherland facility. are available. Above the main entrance to the museum is the Oculus, where unimpeded The headquarters at Cape Town is 10Your local space sunlight streams through a circular sky- recognized as a National Heritage Site light, marking the passage of time like a and is accessible to visitors on Open museum or planetarium sundial. On the right side of the building Nights, which occur every second and is the planetarium theater, which is fourth Sunday of the month. Guests can Can’t make it far from home? housed in a sphere with minimal visible view a presentation on physics or astron- That’s okay! Check nearby cities for support. The effect is meant to invoke the omy, tour the museum and library, and astronomical exhibits or planetariums illusion of weightlessness. And finally, a observe through the McClean Telescope to enjoy. And, if all else fails, you always visitor’s experience culminates at an on clear nights. have access to the real deal just above inverted dome offering a view of the sky your head! — a real encounter with the universe after a mostly simulated experience. Caitlyn Buongiorno is associate editor of Astronomy. Permanent exhibits include a walk- through of the history of the universe, human exploration, and China’s astro- nomical records; an interactive “Journey to Mars” virtual reality experience; and a 78-foot (24 m) solar telescope. ABOVE: The Daniel M. Soref Dome Theater and Planetarium is Astronomy’s local destintation. TONY SAVINO/DREAMSTIME BELOW LEFT: The Shanghai Science & Technology Museum’s Shanghai Planetarium is the largest astronomy museum in the world. ARCH-EXIST BELOW RIGHT: The South African Astronomical Observatory’s Sutherland facility is home to the South African Large Telescope (SALT), the 1.0-meter and 1.9-meter telescopes, and the Lesedi 1-meter telescope. SAAO/JANIK ALHEIT Shanghai Planetarium • Shanghai, China SAAO • Cape Town, South Africa

SEE FALL’S BEST Messier objects Take in 20 sights in just one night. BY MICHAEL E. BAKICH M74: SERGEY TRUDOLYUBOV. M14: FERNANDO OLIVEIRA DE MENEZES

spring Let’s get 13'. You’ll find this often M28: FERNANDO OLIVEIRA DE MENEZES. M21: DAN CROWSON. M29: RICHARD HAMMAR. M31: DREW EVANS. M39: SARA KHALAFINEJAD. M72: DAN CROWSON (April 2021 started overlooked Messier object issue) and 2.6° southwest of Mu (μ) summer Our first tar- Sagittarii. You’ll definitely (August get is globu- spot the Trifid Nebula (M20) 2021 issue), lar cluster first. When you do, look here is your M14 in slightly northeast for M21. agenda for Ophiuchus, A 6-inch scope reveals two autumn. And, which is dozen stars brighter than unlike partici- neither faint 12th magnitude. The pating in a full (magnitude 7.6) 7.2-magnitude star SAO Messier marathon, nor small (11.7'). 186215 shines at the cluster’s you won’t have to stay However, it lies center. up all night for this one; in a part of the you can view all 20 of these sky far from The third object on our objects between the time it any bright star. list, M24, also known as the gets dark and midnight. To find it, start Small Sagittarius Star Cloud, I’ve listed the objects in at Gamma (γ) Ophiuchi and is an asterism. Start by find- order of right ascension, move 6.5° south-southwest. ing it through binoculars 3° which means the first will Through a 4-inch scope at north of Mu Sagittarii. At be farthest west and the fol- 100x, you’ll see a tight sphere magnitude 4.6, it’s relatively lowing objects will set in that’s not easy to resolve. bright, and it measures a order after it, giving you Then crank up the power and whopping 95' by 35'. At M24’s more time to observe each. see if you notice that it’s not northwest end is NGC 6603, In 2022, the Moon is New perfectly round; it appears a magnificent open cluster on Sept. 25 and Oct. 25. So, slightly stretched in an east- of several dozen stars. And your first observing window west orientation. while you’re in the area, runs from around Sept. 18 to Next, look for open cluster look 1° west-northwest for Sept. 27. Starting Sept. 28, M21 in Sagittarius. It glows Barnard 92, a dark nebula stray moonlight will interfere at magnitude 5.9 and spans shaped like a fingerprint. with your search until Last t’s been six months Quarter, which occurs on since astronomy clubs Oct. 17. Then the sky will around the globe stay Moon-free until past hosted events for the midnight for another week, Messier marathon. marking your second observ- The goal of this single- ing window. Be sure to let night observing challenge your scope cool to the ambi- is to catch all 109 deep-sky ent temperature, objects in French comet- take your time hunter Charles Messier’s with each object, famous catalog. and have fun! Due to the way these celestial gems are positioned in the sky, there is only a brief span from mid-March to early April when all the objects are visible over the course of a single night. But even if you missed the last full marathon experience, you can keep your observa- tional muscles in shape by giving this mini-marathon a try. In the spirit of my mini- Messier marathons for 46 ASTRONOMY • OCTOBER 2022

The 6.9-magnitude open globular, magnitude 7.6 M69. initially thought this object cluster M18, which you’ll Through an 8-inch scope, was a comet. The globular find 4.2° north-northeast of you’ll have to look carefully cluster glows at magnitude Mu Sagittarii, is up next. A to resolve any of the stars 9.3 and spans 5.9'. You’ll 4-inch telescope reveals about packed in its 9.8' diameter. find it 3.3° southeast of a dozen stars in a region 10' Its core appears broad but Albali (Epsilon across. Take it easy on the concentrated, and it is sur- Aquarii). Most of power — higher magnifica- rounded by a thin halo. M69 M72’s stars lie tions spread the cluster out so lies in a rich star field, so close to its core, much that it gets lost among crank up the power to see which accounts the background stars. it best. for three-fourths of the cluster’s Our second globular Our next target, M29, lies diameter. To spot on the list (often ignored in Cygnus. Although it’s rela- the outliers, because spectacular M22 tively bright (magnitude 6.6), use a mag- resides nearby) is M28 in it’s one of the most difficult nification Sagittarius. It glows at mag- objects on Messier’s list to of 200x or nitude 6.8 and boasts a diam- identify because it’s a loose higher. eter of 11.2'. Look for it 1° open cluster only 6' wide that northwest of Lambda (λ) sits in front of a rich Milky Sagittarii. An 8-inch scope Way star field. To find it, will resolve several dozen look 1.8° south of Sadr stars in its wide halo. (Gamma Cygni). A small Through a 14-inch scope, scope works best because your star count will climb it won’t reveal the myriad to more than 150. High- surrounding stars. power views of the core unlock its three-dimensional When you move on appearance. to observing M72 in Aquarius through a Next, look 2.5° northeast small scope, of Kaus Australis (Epsilon you can see [ε] Sagittarii) for another why Messier 47

Also located in Aquarius, Now head 8-inch scope will reveal this view, which includes M31’s M33: PATRICK WINKLER. M76: DAN CROWSON. M45: KASRA KARIMI. M77: DAN CROWSON M73 resides just 1.2° east of north and magnitude 6.9 cluster to have nucleus, dust lanes, and two M72. With a magnitude of find open some 75 stars ranging from companion galaxies (M32 8.9 and angular diameter of 9th to 12th magnitude and NGC 205), or crank up just 2.8', M73 is nothing cluster M39 packed within about 13' the power and take in small more than an equilateral tri- in Cygnus. across. Although there are regions at a time. Especially angle of stars with a fourth It glows at lots of stars in the field, M52 look for bright clumps in star lying just to the north- magnitude is easy to spot. Look for the M31’s spiral arms that mark northwest. That Messier 4.6 and prominent clump of six stars sites where new stars are thought that this pedestrian sports a on its eastern edge. forming. grouping could be confused diameter for a comet proves how prim- Next up is the magnificent Neighboring Cassiopeia itive his telescope was. It’s all of 0.5°. To spiral M31, also known as holds our next target, M103. right to take a quick glance locate it, the Andromeda Galaxy, This magnitude 7.4 open and check this object off point your along with its satellite, ellip- cluster lies 1° northeast of your list. telescope tical galaxy M32. The latter Delta (δ) Cassiopeiae. M103’s 2.8° north-northeast of object glows at magnitude 8.1 bright stars stand out against Rho (ρ) Cygni. Look closely and lies 0.4° south of the the rich Milky Way. The 40 through a low-power eye- center of M31. But at 8' by 6', members range from 8th to piece. M39 is so big that it’s M32 is not the standout in 13th magnitude and are easy to lose among the rich this part of the sky. grouped in a tight triangle Milky Way background. You 5' on a side. should be able to count two M31 glows at magnitude dozen stars brighter than 3.4, bright enough to spot The compact trio of stars 12th magnitude. from a dark sky without that make up the constella- Move to Cassiopeia for optics. It’s also huge, measur- tion Triangulum holds one of our next target, open cluster ing 185' by 75', an area the sky’s true wonders: M33, M52. Find it by tracing a line greater than a dozen Full also known as the Pinwheel from magnitude 2.2 Alpha Moons. This star city is the Galaxy (not to be confused (α) Cassiopeiae to magnitude nearest large spiral to our with M101, also often called 2.3 Beta (β) Cas. The dis- Milky Way, and it sits at the the Pinwheel Galaxy). This tance between those stars is far end of the Local Group of magnificent spiral glows at 5°. Continue another 6° and galaxies. To observe it, either magnitude 5.7 and measures you’ll land on M52. An use low power for an overall 67' by 42'. Despite its listed magnitude, this galaxy has a low surface brightness. Binoculars will reveal its shape, but the best approach is through a 12-inch or larger telescope. Find emission neb- ula NGC 604, which sits at the end of M33’s northern spiral arm. Crank the magni- fication past 200x and look for two tiny lobes in contact. Next is the magnitude 9.4 spiral galaxy M74 in Pisces, which measures 10' by 9.5'. You’ll find it 1.3° east- northeast of Nu (ν) Piscium. An 8-inch scope will reveal the uneven spiral arms and the mottled halo around M74’s bright core. Several stars located much closer to Earth are superimposed on the galaxy. Our next object is this list’s only planetary nebula, M76 in Perseus. It’s dim 48 ASTRONOMY • OCTOBER 2022

(magnitude 10.1) and small at magnitude 8.9 and mea- field of view. M45 seems (65\"), but certainly worth sures 7' by 6'. You’ll find it most pleasing to the majority a high-powered look. less than 1° southeast of Delta of amateur astronomers Also known as the Little Ceti. When you observe it, through 10x binoculars. Dumbbell, it can be found spend your time searching 1° north of Phi (ϕ) Persei. An the disk that surrounds it for OK, it’s your turn now. On 8-inch scope will show you signs of mottling. Through the next clear and moonless the two lobes that gave the large scopes, look for the gal- night, set up your scope, get nebula its common name. If axy’s tightly wound spiral comfortable, and use this list you have access to a 16-inch, arms, the brightest of which to help you run the fall you might spot some of the lies southeast of its core. Messier mini-marathon! large, diffuse halo that sur- rounds M76’s inner region. Finally, we arrive at M45 Michael E. Bakich is a in Taurus, the Pleiades. At contributing editor Next up is open cluster magnitude 1.6, it’s the sky’s of Astronomy. M34 in Perseus. At magni- brightest star cluster. Why tude 5.2, it’s bright enough Messier included it in his cat- for most amateurs to spot alog of cometlike objects, without optics from a dark we’ll never know. M45 is also site. Look for it 5° northwest known as the Seven Sisters, of Algol (Beta Persei). A but naked-eye observers with 4-inch scope lets you count good vision, patience, and a more than 30 stars in an area steady sky often see more 35' across. At 100x, look for than seven stars in the 110'- chains of faint stars looping wide cluster. How many can across the field of view. you count? Telescopes reveal fainter stars throughout the Our penultimate target for cluster but also spread them this mini-marathon is spiral out, so fewer populate a given galaxy M77 in Cetus. It glows

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