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musemuse® JULY/AUGUSTJULY/AUGUST 22017017

TOTAL viewing guide + much more muse¨ JULY/AUGUST 2017 VolumeVolume 221, Issue 06

FEATURESFEATURES

10 Ready, Set, Eclipse An observer’s guide by Meg Thacher

20 27 28 36 40 I Saw the Eclipse— There She Blows! So Long, The Truth A Mission to from Space! ’s Cassini ’s mission is about Discover Our Past Students launch a Europa is in the coming to an end. Why did it lose its One special asteroid high-flying project. news. by Rachel Zimmerman “” status? may hold the key. by Nick D’Alto by Mara Johnson-Groh Brachman by Charles C. Hofer by Stephanie M. Bucklin CONTENTS

DIRECTOR OF EDITORIAL James M. “Bosun” O’Connor EDITOR Johanna “Sunporch” Arnone DEPARTMENTSDEPARTMENTS CONTRIBUTING EDITOR Kathryn “Tsunami” Hulick COPYEDITOR/PROOFREADER Meg “Sunflower” Moss ART DIRECTOR Nicole “Gesundheit” Welch 2 Parallel U: “Pigmentamorphosis” DESIGNER Pat “Sunfish” Murray by Caanan Grall DIGITAL DESIGNER Kevin “Unsung” Cuasay 7 RIGHTS & PERMISSIONS David “Sundae” Stockdale Muse News by Elizabeth Preston BOARD OF ADVISORS 16 Infographic: ONTARIO INSTITUTE FOR STUDIES IN EDUCATION, Anatomy of a Star UNIVERSITY OF TORONTO Carl Bereiter by Meg Thacher ORIENTAL INSTITUTE, UNIVERSITY OF CHICAGO 18 John A. Brinkman Science@Work: Marla Geha NATIONAL CREATIVITY NETWORK by Peg Lopata Dennis W. Cheek 24 Mini-Myth: Hey, Bring COOPERATIVE CHILDREN’S BOOK CENTER, A LIBRARY OF THE SCHOOL OF EDUCATION, UNIVERSITY OF Back Our ! WISCONSIN–MADISON K. T. Horning by Carrie Clickard FREUDENTHAL INSTITUTE 32 Jan de Lange Photo Op: FERMILAB The Cassini Gallery Leon Lederman by Rachel Zimmerman Brachman UNIVERSITY OF CAMBRIDGE Sheilagh C. Ogilvie 45 Do the Math: Planet Search by Ivars Peterson Jay M. Pasachoff UNIVERSITY OF CHICAGO 47 Your Tech Paul Sereno by Kathryn Hulick 48 Last Slice by Nancy Kangas MUSE magazine (ISSN 1090-0381) is published 9 times a , monthly except for combined May/June, July/August, and November/December issues, by Cricket Media, 70 East Lake Street, Suite 800, Chicago, IL 60601. Additional Editorial Office located at 7926 Jones Branch Dr, Ste 870 McLean, VA 22102. Periodicals postage paid at McLean, VA, and at additional mailing offices. One-year subscription (9 issues) $33.95. Canadian and other foreign subscribers must add YOUR TURN $15.00 per year and prepay in U.S. dollars. GST Registration Number 128950334. For address changes, back issues, subscriptions, customer service, or to renew, please visit shop.cricketme- dia.com, email [email protected], write to MUSE at Cricket Media, PO Box 6395, 3 Harlan, IA 51593, or call 1-800-821-0115. Postmaster: Please send address changes to MUSE, Citizen Science Cricket Media, PO Box 6395, Harlan, IA 51593. 4 Muse Mail Editorial office, 70 E. Lake Street, Suite 800, Chicago, IL 60601. July/August 2017, Volume 21, Number 06, © 2017, Carus Publishing dba Cricket Media. All rights reserved, including right of reproduction in whole or in part, in any form. For information regarding our privacy policy and 35 Q&A compliance with the Children’s Online Privacy Protection Act, please visit our website at cricket- media.com or write to us at CMG COPPA, 70 East Lake Street, Suite 800, Chicago, IL 60601. by Lizzie Wade 46 Photo credits: C - REUTERS/David Gray; TOC - REUTERS/Yuriko Nakao; 5-6 CPdesign/Shutterstock. Contest: Inventor to com; 5 (RT) CebotariN/Shutterstock.com; 6 (LT) Jennifer Davis, (LB) Laura Dinraths/Shutterstock. com; 7 (TC) Sumukha J. N; 8 (RT) ALEXANDR SOLDATOV/Shutterstock.com, (LC) Korotova Liudmyla the Stars /Shutterstock.com, (RB) Microgen/Shutterstock.com; 9 (RT) Kurt Hickman, Stanford University, (LB) Yu Chen; 10-11 Allexxandar/Shutterstock.com; 12 (LT) Michael Zeiler, greatamericaneclipse. com, (RC) NASA; 13 (LT) Rolf Nussbaumer Photography / Alamy Stock Photo, (RT) RGB Ventures / SuperStock / Alamy Stock Photo, (LB) Arne Danielson/NASA; 14 (LT) © Jay M. Pasachoff, (RB) Photo by Deborah D. Pasachoff; 18 (bkgd) ESA/Hubble & NASA, (BC) Marla Geha; 19 (BC) Eduard MS. ACORN Moldoveanu/ Shutterstock.com; 20-21, 20 (RB), 21 (LT), (RB), 22 (RC), (RB) Eclipse Ballooning Project, (LC) MSU photo by Evelyn Boswell; 20-23 (bkg) Oleg1969/Shutterstock.com; 27 - NASA/ESA/K. Retherford/SWRI; 28-29 NASA/JPL-Caltech/Space Science Institute; 30 (LT) NASA/ Jet Propulsion Laboratory, (RT), (LB), (RB) NASA/JPL-Caltech/Space Science Institute; 31 (RT) NASA/ Jet Propulsion Laboratory-Caltech; 32 (TC) NASA/JPL-Caltech, (RB) Morphart Creation/ STRONGLY RESEMBLES Shutterstock.com; 33 - NASA/JPL-Caltech/Space Science Institute/Kevin M. Gill; 33 (LT), 34 (TC), Cate’s (LB) NASA/JPL-Caltech/Space Science Institute; 34 (RB) REUTERS / Alamy Stock Photo; 36 - NASA mom Issa Pine / Johns Hopkins University Applied Laboratory / Southwest Research Institute; 37 (BC) Santhosh Varghese/Shutterstock.com; 38 (RT) Charles Hofer, (LT) David Roland/Shutterstock. HEIGHT 5'9" com, (LB) Catmando/Shutterstock.com; 39 (TC) NASA; 40 - Jurik Peter/Shutterstock.com; 41 (RT), 42 (LC) PHILIPPE MOUCHE, JONATHAN JACOBSEN AFP/Newscom; 41 (RB) Vector Tradition SM/ AGE N/A Shutterstock.com; 42 (RT) NASA/Joel Kowsky, (RB) Lockheed Martin Corporation; 43 (RC) NASA/ Kim Shiflett, (TC) NASA/GSFC; 44 (TC) NASA’s Goddard Space Flight Center/Conceptual Image FIRST POWERED UP 1983 Lab, (LC) University of Arizona/Symeon Platts, (RC) NASA/Kim Shiflett; 45 (LT) NASA/JPL-Caltech; INTERESTS 46 (LT) Ninya Pavlova/Shutterstock.com. Education, human

Printed in the United States of America. knowledge, the Mnemosyne community, data storage, 1st printing Quad/Graphics Midland, Michigan June 2017 practical jokes From time to time, MUSE mails to its subscribers advertisements for other Cricket Media products or makes its subscriber list available to other reputable companies for their offering ONCE SAID “The mothership of products and services. If you prefer not to receive such mail, write to us at MUSE, P.O. Box 6395, Harlan, IA 51593-1895. won’t be returning for me.” PARALLEL U CAANAN GRALL

2 CITIZEN SCIENCE CAANAN GRALL

To: United States eclipse enthusiasts and Meg Thacher From:

Will you be along the path of totality on August 21? Check the map on page 12! If yes, lucky you! Use the checklist below to get ready. The rest of us may be able to catch a partial eclipse (with solar-viewing glasses) or view the event online or on TV. What to take to the eclipse: ❏ Solar-viewing glasses (sometimes called eclipse glasses) ❏ Pinhole projector (see page 15) ❏ White sheet to see shadow bands ❏ Phone or watch set to the correct time ❏ List of times for eclipse phases ❏ Snacks

Eclipse-viewing tips: ❏ Choose a site that’s not blocked by trees, mountains, or buildings. ❏ Check the weather the night before and the day of the eclipse. ❏ Pick a few alternate viewing sites, and be ready to relocate based on weather conditions. ❏ Arrive early (and plan on heavy traffic). ❏ The eclipse will last two to three hours. Make sure restrooms are available! ❏ If you want to take photos, place a filter or safe viewer over your camera’s lens (and viewfinder, if it has one) as well as in front of your eyes when you look up.

FIVE CHECKING INTO THE THAT WAS ONE I CHATEAU OF FUN SUN PUN RUN HEAR THE MOON GUYS. WHO’S SURE THE PHASES PLEASE! READY FOR A TO ECLIPSE ARE SET TO TOTALITY AMAZING ANY OTHER PLANS STUN! EXPERIENCE? YOU MIGHT HAVE TODAY.

3 Cricket Crossover Event Hello Earthlings, aliens, parakeets, and other strange creatures!

Mail I am a Gravity Falls fan, a parakeet enthusiast, a theater kid, the overlord princess of violin, and a rather devoted Muse reader. If you get Cricket, you

Muse may know me on the Chatterbox as Abigail S. Hi, CBers! Oh, this isn’t the time? Right. Anyway. Besides the fact that Muse is amazebubble and I would like to express my Parallel U fangirl- ness, I am writing to suggest something. During the time of the old Muses (RIP Kokopelli), there was the [online] Muse Townhall, which I enjoyed going on and I miss now. It would be awesome if y’all could resurrect it! I love how Muse is educational and sciencey and Fan art by Hugh P. B. interesting and well written, so ILLUSTRATION it was really fun to discuss the of the articles on the Townhall with my An Artist by Any Other Name fellow science nerds! I would like to start off simply by saying If you decide to toss this letter thanks. Your magazine is marvelous, or magnifique, as they into the FMP, no will say in the land of cheese (France). May I ask some questions come and eat you. No potatoes concerning Aarti, O, Cate, Whatsi, and Ms. Acorn? (Using my will leap onto your heads and do painful jigs in tap shoes. No magical abilities, I can see you shaking your head yes.) OK so multicolored bunnies shall invade number one: does Cate’s hair naturally grow like that or does your personal space. All that will she style with mousse? (Of course, I could ask the same ques- happen is that one 12-year-old tion about Whatsi.) living half in Southern California Number two: if Ms. Acorn is only a hologram, why is it that and half in her imagination will be she clearly has a shadow? I mean, a hologram is a projection a bit disappointed. of light concentrated to form a visual 3D object. If Ms. Acorn —ABIGAIL S. / age 12 is truly a projection of light, she would be completely intan- gible, however, she still manages to do things like hold objects standing on solid ground and HAVE A SHADOW! Let’s Pretend Finally: amazing coincidence! You have abbreviated hot pink Fair tidings! I’m Evan. So, bunnies to “HPBs,” and guess what else HPB stands for? Me! My I came up with this method initials are H.P.B. Before you ask, I am NOT making this up. pretty much about (nothing —HUGH P. B. special) TELEPORTATION! It P.S. Is Ms. Acorn married? all starts with . Nucleus and . Let’s pretend Huge props for your artwork, Hugh! I’ve heard Ms. Acorn’s the electrons are the size of name is actually an acronym, but I’m not sure what it stands an apple. The nucleus would be some thousand feet away. for. (She looks real to me too!) This has puzzled scientists —AARTI 4 for about what the space between the electrons and nucleus is. This could be a fourth source of matter. One day a little super smart birdie came along and told me if wormholes could be a source of transportation that would be revolutionary, but they could only be stabilized with something that’s neither solid, liquid, nor gas. That’s why I’m here. To tell you if that space “Kittens must be is matter, teleportation could be petted, or they a reality. will remain wild —EVAN / age 9 1/2 / Minnesota FOREVER.” P.S. If it is a fourth source of matter, please contact the government!

Thanks for writing I Love Cats nice) and the with Evan. I believe I love Muse and cats! I have gray swirls. I’m just a plain scientists call two cats, Shadow and Blondie. gray dragon. I am NOT an plasma the fourth I get three magazines: Muse, dragon. I’m from planet state of matter. The sun is a Cricket, and Catster. Tripico. It’s millions of light- great big ball of plasma, for I think you should write years away (trust me), so we instance. Does that help with an article on the science of can’t reunite. Now that I think your inventing-teleportation cats. Here are some facts to get about it, that’s probably why project at all? you started: I got my Muse so late last —WHATSI Cats have three eyelids. time. Anyways, I’m going to Kittens must be petted, or be late for the tea party with they will remain wild FOREVER! the hot pink bunnies. Edited for Space (but A tiger’s skin is striped like —THE ANONYMOUS JAY Not Sense) its fur. P.S. Cate, can you somehow On a scale of one to ten, If there are hot pink bunnies visit me? (You’re my favorite!) what’s your favorite color of at Mnemosyne, maybe there the alphabet? Mine is square should be electric blue cats too. Thanks you . . . but many people who have Please don’t throw this letter two—I’m blushing. taken the survey choose a into the fan mail pit. Oh, and by Vanessa, you’ll be strange creature called a WHAT the way my favorite Parallel U the first person I tell ON EARTH?! Never heard of it, character is Cate. if I spot an electric have you? Look at the phrase —VANESSA V. / age 12 / California blue cat. That would be a thrill. “fresh avocado.” What happens if And Anonymous Jay, I’d normally you put the space here: FRE warn someone away from an SHAVOCADO? Try saying it out HPB tea party. They’re notorious. loud. It will seriously make you Just a Plain Gray Dragon But you should be able to hold laugh really hard. Cate, do you Hello human beings! This your own. have a favorite time? IS MUSE cannot be thrown in the FMP!!! —CATE EDIBLE?!!? There ya go. I said I have been trying to contact it. Now: IF YOU THROW THIS my fellow dragons. You see, Something to say? IN THE FAN MAIL PIT, I WILL in a previous Muse, there Send letters to Muse Mail, SEND AN ARMY OF POTATOES was the leafy sea dragon and 70 E. Lake St., Suite 800, Chicago, IL 60601, TO ATTACK MUSE HQ !!! GOT then the dragon with orange or email them to IT? Great! *evil grin* >:) stripes (I know a dragon who [email protected] —THE TOTALLY AMAZING FOX has polka dots but she’s really

5 currently at level 2 (small hits and doughnuts; Craaw the and pushing), and trying to get muse of poetry; Bo, the muse of to level 3, where you can hit reading; and Aeiou, the muse of as hard as you want. So I am technology. There were others, practicing dishing out hits and but my old magazines were receiving them. thrown out. Mail —JULIANNA D. (LOVE POTION #9) (5) Starfishes are not fishes and / age 13 / Alberta, Canada have no brains. (6) And finally, the most important answer: ??????????????? ???????????????!!!! Do not forget Muse Seven Answers to this or you will ?????????!! Questions Unknown (7) FROM, THEO / age 12 I know you new people have some questions. Well, I have all the answers. Here they are: (1) 42. We don’t know the Oculus Engineer question yet. Your magazine is the BEST! (2) A healthy woodchuck can And when I say best, I mean best chuck about four logs per day. in the whole stinking multiverse Go Wipeouts! (3) The HPBs, or hot pink of magazines! It seems like I was so excited when bunnies, were a tactic employed whenever I get into something I found a roller derby by the original Muses during the scientific, you publish a whole article in your magazine! cat-dog war. They worked like issue on it. When I got into Never before have I seen an this: if there was any statement relativity, you published an article about roller derby in about the superiority of cats issue on it. When I got into a magazine before. I actually over dogs or vice versa, it would sustainable cities, you published play on a junior roller derby be replaced by hot pink bunnies. an issue on it. When I got into team so it was pretty cool (4) The original Muses were: virtual reality, you published to see the sport that I play Kokopelli, the muse of pie a whole issue on it. What are in a magazine! I am in my throwing and trickery; Chad, you doing? Stalking me with fifth season of junior derby the muse of science; Urania, HPBs? When you published the with the Lethbridge, Alberta, the muse of ; October 2016 issue, it got me Windy City Wipeouts. I am Feathers, the muse of farming into virtual reality even more. It got me into VR so much that “Starfishes are not fishes I rallied all my grandparents and have no brains.” and parents into getting me an Oculus Rift for my birthday. It’s SO COOL! I truly do think that it’s the future of entertainment, sports, and so much more. Also, could you guys please do an issue on engineering? It’s what I want to be when I’m older. Maybe you could do a few engineering challenges? Thanks. —THAT DUDE FLYING AROUND IN VR / age 12 / Florida P.S. O’s my favorite muse.

Dude! You’re my favorite reader. Or one of my favorites, at least. See you in VR! —O

6 text © 2017 by Elizabeth Preston Muse News I Sorting-Hat Spider Sorting-Hat Harry Potter andthe BY ELIZABETHPRESTON of the books they love—and the magical world of world real-life magical the love—and they bugs. of books the spider new the named scientists the hat’sSo Gryffindor. Godric cofounder school was owner original The student of the in. four houses which belongs announces hat the hat.Then to putmagical on has this school wizarding PotterHarry books. ACCIO ARACHNID In student J. new arriving at K.Rowling’s every series, thought it just looked thought like“sorting the from the hat” didn’tshape only remind also of scientists They the aleaf. stayday. during camouflaged the But spider’sthe odd helps it This leaf. like adead that looks back apointed and of spider. species new little The brown critter has spiny legs n aforest in southwestern researchers India, discovered a

Eriovixia gryffindori Eriovixia , in honor honor in , The answerison spot whichone? F these stories is ALSE page 45. Oneof . Canyou PHYSICS Solar Flair WISH YOU were a little taller? If you live in the path of this summer’s solar eclipse, you can take

News advantage of a neat light-bending effect to give yourself a boost. People living in some parts of the United States will be able to witness a total solar eclipse on August 21. In this rare event, the moon

Muse briefly blocks our view of the sun. Just before the sun is totally covered, a phenomenon called the Gregory-Jordan effect will occur. The last weak sliver of sunlight, warped by passing through Earth’s atmosphere, will cause objects to appear vertically stretched. As a result, a photo taken at exactly the right moment will make a person

look 13 to 15 percent taller. Get those selfie ANIMAL BEHAVIOR sticks ready! Why Did the Pigeon Cross the Road? . . . Because it didn’t care that there was a car coming! City animals are often in danger of getting squashed by traffic. But if they watch lots of cars, trucks, and buses speed past, maybe they learn to keep their distance. Scientists tested pigeons to find out if this is true. They used birds that had grown up in a barn and never seen traffic. First, the researchers put the pigeons in cages next to a road and zoomed past them in a pickup truck, over and over. Then they tested the birds in a virtual traffic simulation. The pigeons watched a video of a truck that looked like it was about it hit them. Researchers measured how quickly the pigeons got scared and flew away. Pigeons that had been trained with a real truck were less afraid, not more. So much for street smarts.

SPORTS A Secret to Faster Swimming USING COMPUTER models, 3D-printed plastic arms and hands, and a tunnel, researchers discovered that freestyle swimmers can speed up by slightly spreading out their fingers. Spacing the fingers 10 degrees apart creates more drag, or pull against the water, than holding the fingers together. 8 TECH DESK Old Toy Gets a New Spin A CENTRIFUGE (SENT-ruh-fyooj) is a basic tool in medical labs. It’s a machine that spins very quickly. When doctors spin a tube of blood in a centrifuge, the blood separates into different components, like salad dressing before you shake it up. This lets doctors examine the blood or test it for diseases. But these expensive tools are hard to get in some parts of the world. Now researchers have come up with a (very) cheap solution, based on a toy. The team got inspiration from a toy called a whirligig or buzzer. It’s a disk or button that spins on a loop of “paperfuge” holds tiny tubes on a toy for just a minute and a half can string. Kids around the world have disk made of paper. When a user separate blood. The invention, which played with these for pulls the handles, the disk spins at costs only 20 cents to make, could thousands of extreme speeds—up to 125,000 become a practical tool for doctors years. The new rotations per minute. Twirling the around the world.

PALEONTOLOGY From Toothy to Toothless LOSING YOUR baby teeth younger dinos had a mouth can be awkward. There are full of tiny teeth, they lost gaps in your , your these teeth as they grew up. mouth is changing all the Adult dinosaurs had no teeth time, and biting into an apple at all. Instead, they had Dad’s a is risky. But be glad you’re not smooth beaks. vegetarian, but a dinosaur named The scientists think toothy I’ll chomp lotsa Limusaurus inextricabilis. young dinosaurs dined on things. After this animal lost its baby many different foods, while teeth, it grew a beak. the beaked adults just ate Limusaurus lived about plants. No one knows what 160 million years ago and the tooth fairy put under a walked on two legs. Limusaurus’s pillow, though. Paleontologists studied fossils from 19 Limusaurus specimens of The news different ages. is complete. Go Babies were about to page 45 to see a foot (30 cm) long if you spotted from nose to tail. the false story. Adults were about 5 feet (1.5 m) long. And although babies and

9 READY, SET, ECLIPS An observer’s guide to the August 2017 eclipse

10 he armies battled beneath the hot sun. Neither side seemed to be winning. It was May 28, 585 BCE, the sixth year of war between the Lydians and the Medes in by Meg Thacher what is now Turkey. Suddenly, the light grew thin and the air turned cold. A hole appeared in the sky where the sun should T be, surrounded by a halo of light. Surely this was a sign from the gods that they should make peace. A total eclipse of the sun, as those ancient armies witnessed, could be frightening if you didn’t know it was coming. That fear could even stop a war! Nowadays, we know what causes eclipses. We can predict when and where they’ll happen, down to the minute and mile. Instead of frightening people, an eclipse can bring millions of us together in a wondrous moment of awe. SE! What Causes an Eclipse? Earth the sun, and the moon orbits Earth. The moon passing between the sun and Earth causes a solar eclipse. Although the moon is 400 times smaller than the sun, it’s 400 times closer to Earth. That means they look the same size when viewed from Earth. During an eclipse, the moon casts a fuzzy shadow on the Earth. The center part of the shadow is called the umbra; people in the umbra see a total eclipse. For these viewers, darkness falls as the moon entirely covers up the sun. The gray, fuzzy part of the shadow is the penumbra; people here see a partial eclipse. The farther you are from the center, the less sun is covered up. The moon takes about 27 days to the Earth, but we don’t have eclipses every month. That’s because the moon’s orbit is tilted five degrees to our orbit around the sun. So the moon is often too high or too low when it’s between us and the sun. An eclipse happens only when the sun, the moon, and Earth line up perfectly. The moon’s orbit is an ellipse (oval), so sometimes it’s closer to us and looks bigger, and sometimes it’s farther away and looks smaller. If it appears too small to completely cover the sun, we’ll see an annular eclipse, where a bright ring of light is visible around the moon. When the moon is on the opposite side of Earth from the sun, we may experience a . If the sun, Earth, Mark your and the moon line up right, the will cross into the calendar for the Earth’s shadow. Because Earth’s shadow is bigger than the Great American moon’s, we see lunar eclipses more often than solar ones. Eclipse: Where and When to See the Eclipse On the morning of August 21, 2017, a total solar eclipse will August 21, start in the middle of the Pacific Ocean. It will hit land in 2017 Oregon, run diagonally through the United States to South Carolina, and end in the Atlantic Ocean. Everyone else in

11 What You’ll See James Lowenthal is a vice president of the American Astronomical Society and a member of its Solar Eclipse Task Force. He’s seen three total, two annular, and many partial eclipses. He says a total solar eclipse is “a deeply moving sight.” When the eclipse starts, put on your eclipse glasses or use a safe viewer. Careful observers will see the moon take a little bite out of the sun. If you’re not using a safe eclipse viewer to look at the sun, you won’t notice anything. But about 30 minutes into the eclipse, the light will look . . . thinner. “We know how bright it should be with the sun in a clear blue sky,” says Lowenthal, “but it’s somehow not bright enough.” Because the sun is a crescent, it

North America and people in Hawaii and parts of South America will be able to see a partial eclipse. A total solar A solar eclipse happens when the sun, the moon, eclipse hasn’t occurred the United States since 1979! and Earth line up like this. The map above has horizontal yellow lines that tell you how much of the sun will be eclipsed. The path of totality (where you can see a total eclipse) is a wide yellow stripe. The vertical green lines tell you what time you’ll see the eclipse. For example, Boston will see a partial eclipse at 2:47 p.m. (14:47 on a 24-hour clock). Denver will have a slightly darker partial eclipse at 11:47 a.m. The next total solar eclipse in North America will be on April 8, 2024; its path will run south to north. The 2017 and 2024 eclipse paths cross in Carbondale, Illinois. Those lucky folks have a chance to see a total eclipse twice!

LOCAL ECLIPSE TIMES FOR MAJOR CITIES ON THE PATH OF TOTALITY Eclipse Totality Maximum Totality Eclipse Location Begins Begins Eclipse Ends Ends Duration Salem, OR 9:05 AM 10:17 AM 10:18 AM 10:19 AM 11:37 AM 1m 57.6s Casper, WY 10:22 AM 11:42 AM 11:43 AM 11:45 AM 1:09 PM 2m 28.3s Lincoln, NE 11:37 AM 1:02 PM 1:03 PM 1:03 PM 2:29 PM 1m 25.3s Jefferson City, MO 11:46 AM 1:13 PM 1:14 PM 1:15 PM 2:41 PM 2m 29.9s Nashville, TN 11:58 PM 1:27 PM 1:28 PM 1:29 PM 2:54 PM 1m 58.2s Greenville, SC 1:09 PM 2:38 PM 2:39 PM 2:40 PM 4:02 PM 2m 12.7s Columbia, SC 1:13 PM 2:41 PM 2:43 PM 2:44 PM 4:06 PM 2m 29.7s Charleston, SC 1:16 PM 2:46 PM 2:47 PM 2:47 PM 4:09 PM 1m 42.5s

12 MY ECLIPSE STORY by Jay Pasachoff appears a little skinnier than usual, and shadows will look sharper. And if you look under the trees, you’ll notice that I saw my first solar eclipse as a college freshman 57 the circles of light you usually see are now crescent shaped! years ago, from an airplane over the Atlantic just off As the moon covers more of the sun, it will get darker the Boston coastline. Since then, I’ve seen 64 additional out, and the will drop. Animals will start solar eclipses. My interest in studying the sun at getting ready for night. Birds will roost. A few minutes eclipses has taken me all over the world. I’ve seen 33 before totality, you may see shadow bands—wiggly stripes total eclipses so far, from the Arctic, from an airplane overflying the Antarctic, from Africa, North America, of light and dark that move quickly across the ground. South America, Asia, and Europe. And from some mid- These may occur when the light of the thin crescent sun ocean islands and ships. But I have never seen a total comes through the Earth’s wiggly atmosphere. Then, eclipse from the United States mainland. look west. You’ll see darkness, “as if it’s night over there To be outdoors as the universe around you darkens, and it’s daytime where you are,” says Lowenthal. This is with the light turning eerie and shadows sharpening in the shadow of the moon rushing toward you at over a way that makes you uneasy, is the most remarkable 2,000 miles (3,200 km) per hour. experience I have ever witnessed. So I am very much When you can’t see the sun at all through your eclipse looking forward to this all-American eclipse that crosses glasses, it’s safe to take them off. You may see Baily’s Beads, the continental U.S. from West Coast to East Coast for little specks of sunlight shining between the mountains on the first time since 1918. the moon. Then you’ll start to see the corona—the sun’s As an eclipse , I have enjoyed hospitality from colleagues all over the world when viewing outer atmosphere—around the moon and one final bead of eclipses in their countries, so now it is our turn to sun shining through. It’s known as the diamond ring effect. be hosts. And my children, who started seeing total Because it’s only dark where you are, you’ll see something eclipses when they were two years old and a few like a 360-degree sunset. old, respectively, will now be joined by their During totality, the corona appears like a bright crown children. We will also be joined by my professional team around the black disk of the moon. The corona is about as of astronomers and students from countries around the bright as the full moon. It’s shaped by the sun’s magnetic world, astronomers who are coming with their families fields, and it’s different every eclipse. We see its inner region for the spectacle, and others. only with a special telescope or during a total eclipse. I looked at maps showing statistics of cloudiness As your eyes adjust to the darkness, you’ll see on August 21sts from the last couple of decades and prominences at the moon’s edge. You’ll see stars and decided to observe the eclipse from Salem, Oregon. But statistics are not reality, and we can but hope for clear weather for our group and for all the people across the country and the continent, especially for those in the path of totality as it passes through parts of 14 states. My colleagues and I have devoted a lot of time to spreading the word about how exciting it is to be outdoors to experience totality firsthand, and we hope you get a chance. If all you can see is a partial eclipse where you are, perhaps you can try again in 2024, when the zone of totality will travel from Mexico up through the eastern United States and into eastern Canada. Happy observing!

Jay Pasachoff is Field Memorial Professor of Astronomy at Williams College in Massachusetts.

13 It is not safe to view the eclipse through things like sunglasses, potato chip bags, DVDs, or smoked glass. Even if they look dark, they could be letting in ultraviolet light. You can’t see it, but UV light will harm your eyes. If you look through a telescope, binoculars, or a camera, it’s even more important to have a filter on the main lens. You can place a pair of eclipse glasses on your phone’s camera. But, Lowenthal says, “you don’t want to fiddle with equipment too much—enjoy the experience of totality.”

PINHOLE PROJECTOR The simplest pinhole projector is made of two white paper plates. Poke a tiny round hole in one of them using a thumbtack. Standing with your back to the sun, hold the In this edited, layered photo, the sun’s corona surrounds the plate with the hole at about shoulder height. Place the dark circle of the moon. Pasted in the center of the dark circle intact plate in its shadow. The pinhole will project an is a filtered image of the sun that shows magnetic activity. of the sun on the bottom plate. (Don’t look through the Around the outside, in red false color, are outer coronal streamers as viewed from a special spacecraft camera. pinhole at the sun!) You can make a fancier pinhole camera using a shoebox. Look for natural pinholes (like trees) during the eclipse. in the sky. And all too soon, you’ll see the diamond Or try lacing your fingers together, and see how many ring again, this time with the single bright bead on the other eclipse images you can make on a white surface. Try side of the sun. You may see shadow bands again, and the punching out your name or a pattern in the paper moon’s shadow running off to the east. plate projector. The eclipsed sun will suddenly be bright again. You’ll You can also draw the eclipse, journal it, and share it need to put your eclipse glasses back on to protect your on social media. eyes (cover up cameras and telescopes with correct filters Here’s hoping you get to see the eclipse of 2017. Where too!). The birds will wake up and start singing as if it’s will you be for the eclipse of 2024? morning. The light will get stronger. When the last little bite of the moon disappears, everything will be back to normal. Meg Thacher is a 52-year-old astronomer who has never seen a total If you’re not on the path of totality, you may still see eclipse live. She will be in the path of totality on August 21. the partially eclipsed sun and crescent shadows under the trees. You may observe a temperature drop, weird animal behavior, and planets in the daytime sky. But if you are able to get to the path of totality, you should—there’s nothing else like it! How to Observe Safely You should never look directly at the sun, even if the moon is blocking most of it. Your eye’s lens focuses light on your retina (the part that detects light). And because the retina doesn’t have any pain receptors, you can hurt your eyes without even knowing it. There are two simple ways to see an eclipse without risking damage.

SOLAR-VIEWING GLASSES These are not sunglasses! They’re usually made of cardboard, with special filters that block out 99.99 percent of the sun’s light. Make sure your solar-viewing glasses (or eclipse glasses) meet the ISO 12312-2 standard. The three companies that make approved glasses are Thousand Optical, Rainbow Symphony, and American Paper Optics. Before using them, hold them up to an indoor light to look for scratches and holes. If you find any, throw those glasses out!

14 text and art by Caanan Grall INFOGRAPHIC BY MEG THACHER JOHN GORDON-SWOGGER

SUNSPOTS are magnetic storms. They look dark because they’re S cooler than the URF photosphere. They AC can be 10 times the E E size of Earth. R E H P CO S NV O E T C O T H P N RAD Z I O AT IV N E E Z O N CO E R E

FILAMENTS are squiggles of cool gas in the .

16 ANATOMY OF A STAR ÝÝ Most stars are so far away that it takes years for their light to get to us. But sunlight is only 8 minutes away (93 million miles, or 150 million kilometers). We can learn about other stars by studying the sun close up.

CORE 27 million0 F (15 million0 C) ➜The sun is powered by nuclear fusion. In short: hydrogen atoms smash together to make atoms. Each helium has a little less mass than the hydrogen atoms it formed from. That mass difference turns into a A CORONAL MASS EJECTION lot of energy. (CME) happens when gas blasts off the sun’s surface RADIATIVE ZONE at 186 miles (300 km) per 13 million0 F (7 million0 C) second. If a CME hits the to 4 million0 F (2 million0 C) Earth’s atmosphere, we see the ➜ In the radiative zone, photons beautiful aurora, also called (tiny of light) carry northern and southern lights. energy outward from the core. [INSIDE THE SUN] Each photon takes about a million years to get to the convection zone!

CONVECTION ZONE 3.6 million0 F (2 million0 C) E 0 0 R to 9,800 F (5,400 C) E ➜Here, hot bubbles of gas rise H P to the sun’s surface, cool off, S and sink back to the bottom of O A the zone to heat up again. M N O O R R PHOTOSPHERE H O 10,0000 F (5,5000 C) C C to 72000 F (40000 C) ➜This is the part of the sun we see every day. This illustration shows the sun’s surface as seen through a filter, making the chromosphere visible. The photosphere is underneath the chromosphere.

CHROMOSPHERE 10,0000 F (5,5000 C) to 35,0000 F (20,0000 C) ➜The chromosphere is visible with a special filter that lets in only red light. During a solar eclipse, it appears as a faint red ring around the moon. [SUN’S ATMOSPHERE] [SUN’S CORONA 1.8 million0 F (1 million0 C) or more PROMINENCES are filaments seen from the side. During an eclipse, ➜Unless you have a fancy X-ray they look like red loops sticking out telescope, the corona is only from behind the edge of the moon. visible during a solar eclipse. It is a million times fainter than the photosphere. The corona is made of very energetic electrons and streaming out into space. 17 Work @ Science

by Peg Lopata MARLA GEHA ASTRONOMER

Marla Geha works at Yale University in New Haven, Connecticut. In addition to teaching astronomy, Geha studies the formation, evolution, and destruction of dwarf galaxies. Dwarf galaxies are the most abundant type of galaxy in the universe, but they’re difficult to detect because they’re not very bright and are—as the name suggests— small in size. Maybe you wouldn’t think someone needs to use the world’s largest telescopes to study the universe’s smallestt galaxies, but that’s exactly what she does.

18 WHAT GOT YOU WHAT PROBLEMS ARE YOU WORKING ON INTERESTED IN RIGHT NOW? ASTRONOMY? The main question I am working on right now is measuring the I liked math and physics mass or weight of the faintest or least luminous known galaxies when I was in school, but I in the universe. Many of these orbit around our —the also wanted to travel. Since I galaxy Earth is in. These “ultra-faint” galaxies are several million am an astronomer, I get to do times fainter than the Milky Way itself. Turns out, despite being both. Many of the telescopes I called “dwarf galaxies,” they are not small—but very massive, even use to do research are located though they have so few stars. atop mountains in truly beautiful and remote places, SO THESE “DWARF GALAXIES” MAY NOT BE SO SMALL such as Chile and Hawaii. AFTER ALL?! Right. We think this “extra” mass is due to dark matter. Dark matter SOUNDS EXOTIC is made up of particles that have mass, or weight, but don’t produce AND FUN. WHAT any light. These galaxies have a larger ratio of dark matter to stars— OTHER INVENTIONS, more so than any other galaxies. In other words, these ultra-faint BESIDES TELESCOPES, galaxies have more dark matter given the number of stars they have HAVE HELPED than any other galaxies in the known universe. They are way more ASTRONOMERS LIKE massive than we would expect based on their light. So studying YOU MAKE ADVANCES them may help us to better understand what exactly dark matter is. IN THIS FIELD? That could be important because there’s evidence that much of our By far the most important universe is made of dark matter. invention in my field, besides telescopes, has been camera CAN WE SEE ANY DWARF GALAXIES WITH THE phones. We astronomers use NAKED EYE? the same technology that is Yes, there are two you can see from South America, Australia, or in personal camera phones to Africa. They are called the Magellanic Clouds. These two dwarf take pictures of planets, stars, galaxies orbit around our Milky Way. But they are only visible in the and galaxies. Taking digital Southern Hemisphere. images of the sky has com- pletely changed the questions WHAT’S THE MOST AMAZING THING YOU’VE we ask about the universe. LEARNED ABOUT A DWARF GALAXY? The stars in many dwarf galaxies are very old and were likely formed WOW! SO I CAN USE when our universe was very young. So these galaxies give us a window MY PHONE TO TAKE A into what the universe might have been like 13 billion years ago. PHOTO OF A PLANET OR A STAR? YOUR STUDIES SOUND REALLY OUTTA THIS WORLD! Well, our camera phones are WHAT KINDS OF JOBS MAY BE AVAILABLE FOR much larger than the ones on SOMEONE INTERESTED IN ASTRONOMY? phones many people own. A Astronomy can open doors to so many different types typical camera phone is about of careers. Studying astronomy really means 12 megapixels. Our camera studying physics, math, statistics, and phones are 550 megapixels. computer science. All of these topics are in huge demand now and will ALL THOSE MEGAPIXELS be even more important in the MEAN YOU CAN TAKE future. My students have gotten PHOTOS OF THINGS jobs in a wide variety of places, FAR AWAY AND THE even working on developing IMAGES ARE PRETTY video games. CLEAR, RIGHT? SOUNDS FASCINATING. WHAT DO Peg Lopata is a freelance writer YOU LOVE MOST ABOUT living in Vermont. Her favorite YOUR JOB? galaxy is the Milky Way because I get to choose what that’s her home and her first problems to work on. choice for a candy bar.

Keck Observatory, Hawaii 19 by Nick D’Alto

EclipseROJECT.

Building a New Kind of ÒSpaceshipÓ I Saw theTo do it, student teams must send high-altitude balloons STUDENTS TAKE THE LEAD IN NASA’S ECLIPSEto a region of theBALLOON atmosphere called P “near space.” These ould anything be more amazing than seeing a eclipse watching-devices will travel nearly 100,000 feet, total solar eclipse? How about seeing that eclipse or about 19 miles (30 km) above Earth. Each balloon from space? resembles a kind used in weather forecasting, Des Jardins C Peering down miles above the Earth (higher than says. Filled with helium, it measures 6 feet (1.8 m) in the clouds), you would see not only the moon crossing the diameter on the ground. But the balloon will expand to face of the sun, but also the shadow of the moon racing across over 30 feet (9 m) across when it reaches near space oceans and continents, silhouetted against the blackness of because the lower air up there allows the helium space and the curving horizon of Earth. But you’d need to be inside to expand. “Then, past about 100,000 feet,” she says, an astronaut to see something like that, wouldn’t you? “the balloon will burst.” Not anymore. On August 21, 2017, hundreds of young Beneath each balloon, several instrument payloads people will see it too. And they’ll share it with the world in will dangle from a long flying line. (“Payload” describes near real time. Welcome to the amazing Eclipse Ballooning something a vehicle carries for its purpose or mission.) Project, in which teams of students across the United States “Two of these will watch the eclipse: a digital camera to will launch devices high into the air to observe the Great capture still images and a video camera, which records in American Eclipse in a whole new way. They will capture HD,” says Des Jardins. Both are controlled by Raspberry photos and videos as the eclipse sweeps the nation and Pi, low-cost, credit card–sized computers you might use then send them back to Earth. in school science projects. Both are also equipped with “It’s really a golden ,” says Angela Des Jardins, director of the Montana Space Grant Consortium and head of the project. “And it’s all about emerging technologies coming together. Like miniature radio, The still image technology from drones, and the ability to stream live payload uses video.” The Montana program is part of NASA’s National a Raspberry Pi Space Grant College and Fellowship Program. Combining and Pi Camera to take, store and these various forms of tech will accomplish something transmit images historic. “We’ve seen a few eclipses from the International via a modem. Space Station,” Des Jardins notes, “and from single high- altitude balloons. But continuous, real-time coverage of an eclipse from off Earth has never been done before.”

20

Teams built and tested high-altitude balloons during workshops at Montana State University.

To “catch” the data its balloon transmits, each team will operate its own ground-based tracking station. —fromThese tinySpace! mission controls include a directional antenna equipped with motors that keep it pointed towards the balloon’s signal. Then each team will automatically upload Eclipse the pictures and videos they receive to the project website. Preparing the Flight Crews How will students accomplish something that would have been impossible the last time an eclipse crossed the United States? Technology, enthusiasm, and hard work. Already, more than 50 high school, college, and university teams This container is have trained for months with their science advisors. ready to house just They’ve learned how to assemble the equipment. Much about any payload. of it is both advanced and super lightweight. Teams have constructed the capsules from Styrofoam! Then they’ve wireless modems (like the ones your smartphone uses), to learned how to get into the air. “It’s not always easy,” Des send the pictures they take down to the ground. Jardins confesses, “especially since half our teams have But wait—how do you point the cameras at the eclipse never launched balloons before.” In test launch videos, from many miles up? In effect, you don’t. “Some commands they shout, “Hold it!” and “Go this way more!” In May can be sent up to the payloads, through their modems,” Des and July 2016, teams from 30 states completed five-day Jardins explains. “But the cameras will still spin around in the wind.” To deal with this, some teams are experimenting with fins to keep the cameras pointing straight. “Others are just filming constantly,” she adds, “As wind whips the cameras around, the eclipse should come in and out of view.” (Boy, could this make viewers dizzy!) “We also need to know where the balloon is at all times,” Des Jardins says, “especially once it leaves visual range.” So a third module uses GPS to track the balloon’s location— with a little help. It uses a modem that can contact a network of satellites in orbit around Earth’s poles.

There's a first time for everything—including balloon launching.

21 EXPLORING THE SPACE BELOW Technically, “space” begins at 62 miles (100 km) above Earth’s can surface. give us Scientists a breathtaking call the view boundary of the the Earth Karman below. Line. Below that, the layer from 12 to 62 miles (20 to 100 km) is called “near space,” or the “upper atmosphere.” It’s a fascinating region of our atmosphere—higher than commercial airliners fly and above most of our weather but—Nick below D’Alto orbiting satellites. By studying near space, scientists may learn more about climate change, and engineers can develop new communications platforms. And traveling to near space Unlike the vacuum of space, near space has air, which means wind and buoyancy. So instead of using rockets, people can explore this region using craft that float or fly. Solar-powered aircraft, giant dirigibles, and high-altitude balloons are just a few of the remarkable devices proposed for exploring this “space below space.”

workshops at Montana State University to build and test Four instrument their systems. Team members have mastered skills from payloads dangle soldering and programming to web design. All the while from a long flying line beneath each they’ve been gearing up for the flight of a lifetime. balloon. Liftoff! Each team has established a flat, open launch site along the eclipse’s path of totality. Teams from outside that zone will travel to their launch points. On eclipse day, balloons What a view! will rise from schoolyards, parks, airports, and golf courses nationwide. “Each team must get their balloon high enough, and far enough, to meet the eclipse as it arrives,” Des Jardins notes. “So timing is key.” She explains that the balloons rise at about a thousand feet (305 m) per minute. That means it would take about 90 minutes to reach 90,000 feet (27,400 m). Balloons may also drift up to 100 miles (161 km) from their launching points, depending on the they encounter. That’s why some teams will set up their tracking stations at a distance from the launch site. The wind may blow the balloons to them. Cut the Rope There’s one more payload instrument on board. “That’s the cut-down module,” Des Jardins explains. When a balloon’s mission is complete, or if it strays into restricted

22 Ever wondered where Earth's atmosphere ends and space begins? Take a look at the Karman Line at left.

shadow as it crosses our planet. Des Jardins says, “It’s looking toward Earth where the magic will happen.” The eclipse’s shadow, called its penumbra, is about 70 miles (113 km) wide. Des Jardins estimates that from the balloons’ heights, a radius of about 100 miles (161 km) will be visible. This viewing area is ideal. “You’ll be able to see where the land is sunlit,” Des Jardins says, “and where it isn’t—where the eclipse is happening. And you’ll see the edges of the atmosphere, glowing. That will be amazingly cool.” Teams will see the eclipse cross lands and landmarks nationwide. In effect, the Eclipse Ballooning Project aims to take Earth’s first eclipse selfies! Illustrators have created images of the Earth from above during eclipses, and NASA has filmed it from space, but we’ve never seen it in real time. Here’s a chance to see an eclipse from a whole new perspective. You Can See It Too Teams will stream images to the NASA website as data arrives. “As it’s happening,” Des Jardins notes, “you’ll be able to visit the site, and see and compare live feeds from different teams’ balloons along the route.” How will the eclipse look as it sweeps toward the Rocky Mountains? (There will be air space, a signal can tell its modem to cut the line. (A a team nearby.) Or as it crosses the Great Plains? (There will tiny cutting wheel does the job.) As the payloads fall from be teams there too.) To find out, visit eclipse2017..gov the balloon, a parachute will open and carry them safely on eclipse day, and see for yourself! back to Earth. If the balloon bursts before the mission is complete, the parachute will open automatically. Having no high-altitude cameras handy, engineer Nick D’Alto will watch the eclipse with a pinhole camera from the ground. Earth’s First Eclipse Selfie These balloons’ cameras aren’t trying to capture images of the sun during the eclipse. (The cameras aren’t telescopes.) Instead, they’ll help us see the eclipse’s

23 MINI-MYTH JESSE TISE

24 25 MINI-MYTH

26 by Mara Johnson-Groh

There She Blows!

magine a frozen, icy world where huge geysers shoot water vapor up higher than the tallest mountains on IEarth. This bizarre landscape exists on Europa, one of Jupiter’s . Europa is one of the few places in our solar system harboring oceans. The moon’s oceans likely contain twice as much water as Earth’s, but they are buried under many layers of ice. This makes them really hard to study, though many scientists want to take a closer look. Oceans are some of the most promising places in our solar system to look for alien life. Using the , astronomers found evidence that giant geysers on Europa shoot up plumes of water vapor. The plumes reach 125 miles (about 200 km) above the surface— more than 20 times the height of Mount Everest. These eruptions allow scientists to see the ocean water from afar. That’s a lot easier than going all the way to Europa to drill through the thick ice. On an average day, Europa is a chilly -260°F (-162°C). So how does this space snowball have a liquid ocean and giant vapor fountains? One theory holds that as Europa travels around Jupiter, the giant planet’s gravity squishes and squeezes the moon, heating up its insides. This keeps the ocean liquid, even though the moon’s surface temperature is so frigid. The heating may also explain the geysers, though astronomers don’t yet know their exact cause. If you want to head to Europa to check out the moon’s natural wonders, don’t get too close: much of the water vapor rains back down on the surface as tiny ice pellets! 27 by Rachel Zimmerman Brachman So Long, Saturn CASSINI’S MARVELOUS MISSION IS COMING TO AN END.

28 f you’re under 20, NASA’s Cassini spacecraft has been in space your whole life. If you’re under 13, Cassini has been orbiting Saturn your whole life. This Irobotic spacecraft is about a billion miles (1.6 billion km) from Earth, learning about Saturn’s rings and moons, watching its storms, and measuring its moons. Scientists have lots of questions about Saturn. Why does Saturn have massive storms that last for months or years? How old are its rings, and how were they formed? Could any of its moons support life? NASA’s Cassini spacecraft is helping scientists answer these questions, and many more. A SPACECRAFT WITH A SPECIAL BLANKET As big as a school bus, Cassini is the largest interplanetary spacecraft that NASA has ever built. Cassini ’s shiny gold-colored foil blanket protects the spacecraft from tiny bits of rock that could damage its sensitive scientific instruments. The blanket also keeps the spacecraft warm in the cold vacuum of space. Some of the layers of insulation are made from materials similar to those in bulletproof vests. The large, white, dish-shaped communications antenna at the top of the spacecraft points toward Earth. Cassini uses the antenna to transmit its pictures and data as radio signals. The signals travel all the way to the Earth-based Deep Space Network—a group of enormous radio antennas located in Spain, Australia, and California. This network also sends commands to Cassini. Traveling at the , the signals sent to and from Cassini can take an hour and a half to traverse the vast distance between the planets. Cassini has 12 different science instruments on board, including cameras, radar, a magnetic field detector, and instruments to figure out which chemical elements are present in Saturn and its moons. Technology has improved a lot in the past 20 years. Cassini ’s one-megapixel camera may not seem very impressive now, but back in the 1990s, when the spacecraft was built, this camera was cutting-edge! Back then, most people didn’t have cell phones or digital cameras. Now almost every cell phone comes with a built-in digital camera. The latest iPhone camera has 12 megapixels. A probe called , built by the , piggybacked on the voyage from Earth to Saturn. It parachuted through ’s atmosphere to take pictures of the moon’s surface. It found that Titan’s surface has mountains and dry rivers and lakes, and its rocks are weathered and rounded. MISSION: EXTENDED Cassini was built at NASA’s Jet Propulsion Laboratory in Pasadena, California. It was launched from Cape Canaveral, Florida, on October 15, 1997. After a seven-year trip through space, it began orbiting Saturn on June 30, 2004. 29 Learn More

You can find out more about the Cassini spacecraft, and see all of the This mission to Saturn has lasted nine images Cassini has taken of Saturn and its rings and moons, at years longer than originally planned. . If you want to Luckily, the spacecraft carried extra saturn.jpl.nasa.gov fuel, and NASA navigators have found follow along with the Cassini ways to conserve it. mission in its final months orbiting Saturn, you can download NASA’s free “Eyes on the Solar System” software at . eyes.nasa.gov

Cassini has captured valuable images of Saturn’s many moons, including this one, called Dione.

team of scientists on the Cassini mission meets to discuss the most exciting science discoveries, as well as important engineering issues. A NASA illustration shows Cassini’s flight path during the final two phases of its mission. The 20 Ring-Grazing Orbits are gray; the CLOSE UP ON RINGS AND MOONS 22 Grand Finale Orbits are blue. The final partial orbit is orange. Saturn’s beautiful rings are made of ice, dust, and rock. Although they stretch as far across as the distance from Cassini was supposed to spend four years orbiting the Earth to the moon, each ring is only a few hundred feet Saturn, from 2004 to 2008. But the mission was so thick. That means they’re extremely thin! Small “shepherd successful that it was granted a two-year extension moons” orbit within the rings. Saturn’s larger moons orbit (2008–2010) and then a seven-year extension (2010–2017). much farther away from the planet. Like the rings, the The spacecraft slowly changes its orbital path around moons are made of ice and rock. Saturn to get a good view of the rings or the moons, since it Cassini took the first close-up images of many of can’t do both at once. Science planners work with planetary Saturn’s 62 moons. It helped scientists discover several scientists to decide what the craft should study over the of the moons. next few months, and navigators figure out how to get Saturn’s largest moon, Titan, is the second-largest Cassini safely into position to collect the pictures and data moon in the solar system, even larger than the the scientists need. Every few months, the international planet ! Titan is the only moon with a dense 30 atmosphere. Unlike Earth’s nitrogen and oxygen pictures of the rings and study Saturn’s weather from atmosphere, Titan’s atmosphere is made of nitrogen closer than ever before. and methane. Scientists don’t think there’s life on Saturn itself, but Cassini’s radar instrument peered through Titan’s some of Saturn’s moons have the conditions necessary thick clouds and haze and mapped Titan’s surface. for life: water, energy, and chemistry. Even the possibility Now we know that Titan has rivers and lakes of liquid of life affects choices about how to conclude Cassini ’s methane and mountains made of ice. mission. As the spacecraft’s fuel runs out, navigators will Because they’re so far from the sun, Saturn’s moons no longer be able to control Cassini ’s trajectory. NASA are very cold. Methane is usually a gas on Earth, but doesn’t want Cassini to accidentally crash land on one of on Titan, it’s a liquid. Substances like water that are Saturn’s moons. If we send a future mission to Titan or liquid on Earth are often rock-hard ice on Titan. But Enceladus looking for life, we want to be sure that it’s not Cassini measurements show that Titan likely has a liquid something that hitchhiked from Earth onboard Cassini! water and ammonia ocean beneath its crust. On Earth, That’s why September 15, 2017, will be the end of an wherever we find liquid water, we find life. Could life era of planetary exploration. Cassini will end its mission survive in the cold, dark, methane-rich environment in a blaze of glory, plunging into Saturn’s atmosphere. The of Titan? craft will send us precious data about the composition Saturn’s sixth-largest moon, Enceladus, has been one of Saturn’s upper atmosphere, as well as measurements of the biggest surprises of the mission. In 2005, when that will let us know the mass (and age) of the rings. Cassini first flew past Enceladus, it detected icy water Then, as the spacecraft enters the atmosphere, it will vapor coming out of the moon’s south pole. It turns start tumbling, and its communications antenna will stop out that this icy plume is feeding one of Saturn’s rings pointing toward Earth. After we lose contact, Cassini will and comes from a liquid water ocean below the moon’s burn up in the atmosphere like a meteor. Saturn’s dense frozen surface. Scientists didn’t expect this. It raises many atmosphere will crush whatever remains. questions: How long has the plume been active? What As the Cassini mission comes to an end, the scientists and will happen if it eventually stops? Scientists are still trying engineers who have spent most of their careers working on to solve these mysteries. the mission will set their sights on other worlds to explore.

ENDING IN A BLAZE OF GLORY Rachel Zimmerman Brachman is an outreach specialist for the Cassini ’s final 22 orbits, dubbed the “Grand Finale,” are Cassini mission to Saturn at NASA’s Jet Propulsion Laboratory in taking place from April through mid-September 2017. Pasadena, California. She earned a master of space studies degree The spacecraft is flying between Saturn’s cloud tops from the International Space University in Strasbourg, France. She and its innermost rings. Scientists get to see close-up lives in the Los Angeles area with her husband and son. 31 BY RACHEL ZIMMERMAN BRACHMAN Op Photo Photo

THE CASSINI GALLERY

The Cassini spacecraft, seen above in an artist’s concept, was named after a French-Italian astronomer. Jean- Dominique Cassini studied Saturn in the seventeenth century. He discovered several of Saturn’s moons (Iapetus, Rhea, Tethys, and Dione) and was the first person to observe the large gap in Saturn’s rings that eis now named after him—the Cassini Division. 32 The farthest astronauts have ever gone in space is to Earth’s moon, 250,000 miles (402,336 km) away. The journey to the moon took a week. Cassini is about a billion miles (more than 1.6 billion km) from Earth. It took seven years just to get there. The journey has lasted 20 years overall. There aren’t any people onboard Cassini. Scientists and engineers on Earth control the robotic spacecraft remotely from Mission Control at the Jet Propulsion Laboratory in Pasadena, California.

Cassini takes pictures in black and white. By putting red, green, and blue filters in front of the camera lens, computers can help create a color picture from these black-and-white images. Cassini also has special cameras that can see in infrared and ultraviolet, beyond the visible range the human eye can see. This false-color view of clouds in Saturn’s northern hemisphere results from combining images from Cassini’s camera.

33 Op Photo Photo

Saturn has seven rings, named alphabetically in the order in which they were discovered. From Saturn outward, they’re D, C, B, A, F, G, and E. The rings are made of ice, rock, and dust.

Julie Webster is Cassini’s manager of spacecraft operations. She’s the mission’s chief engineer. Webster is responsible for the health of the Cassini spacecraft.

Saturn has more than 60 moons. The smallest moons are the size of a sports arena, but Titan is larger than the planet Mercury. 34 text © 2017 by Elizabeth Wade 35

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or email them to Chicago, IL 60601, IL 60601, Chicago, .) Theythought they 70 E. Lake St., Suite 800, Suite 800, St., 70 E. Lake Send them to Muse Have any questions? Have [email protected] Astronomers called the force Muse in astronomy today. today. in astronomy check out the March 2017 issue 2017 check the out March of the knew away about far how supernovas from Earth. were whenBut they calculated distances, that out turned it Earththe and space between the supernovas had stretched they than even expected. more therealizedthat The scientists is speeding One up. stretching now, from years billions of day, willit even be that so grav- fast be able hold to galaxies won’t ity says. De Leo-Winkler together, responsible for this mysteri- energy.” ous acceleration “dark it what sure is, Theystillaren’t they it but that know exactly, makes up almost 70 percent of Thethe scientists universe. who energy dark signs of discovered won a Nobel Prize 2011, and in the mysteries one biggest of it’s the balloon is now the balloon. the Voilà: Weird, right? It gets even gets right? It Weird, That’s not how it not how works That’s So observe? what did Hubble more space that it did before— it space that more just It’s been infinite. always it’s galaxies, thethat space between andstars, planets is increasing. teams of 1998, two In weirder. explod- studying scientists were calleding stars supernovas. (For ontheir more competition to discover the the fate universe, of and occupies more and more and occupies and more more space. Space was once that outside inside balloon expanded. The theuniverse with universe. a larger exist within doesn’t The expand can space into. it is is—it’s alluniverse there infinite.the “If universe contains everything, then nothing be can says. De Leo-Winkler outside it,” all thoseWhere galax- were De Actually, to? ies off racing the galax- says, Leo-Winkler moving all. at “Theies weren’t the but put, spacegalaxies stay he them isbetween increasing,” describe to prefers explains. He “stretch- this as the universe expanding. than rather ing,” the expandingUnlike balloon, taking any up isn’t the universe

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expanding into? a deflated balloon. As blow you the up, balloon it bigger gets on, says Mario De Leo-Winkler, De Leo-Winkler, on, Mario says an astronomer at the University California,of Riverside.of Think ment “the is expanding.” universe going the right what’s for word telescope, the they faster seemed observation That beto traveling. the in up is summed state- neatly galaxies, he noticed they that from be to movingappeared away Earth. the the farther And away galaxies from him and were his

A & Q THEN ONE DAY IT WASN’T A PLANET. THE END. 36 PlutoThe Truth about by Charles C. Hofer

nce upon a time, Pluto was a planet. The of Science Then one day it wasn’t a planet. The end. Today we take it for granted, but science, as we know it, That might be the world’s worst bedtime has thrived in the Western world for only a little more story. But it’s also 100 percent true. than 300 years. Prior to that, people often guessed at how O Following its discovery in 1930, the natural world worked. The reason the sun rises and little Pluto captured the imagination sets, why birds disappear during the winter months, how of anyone who looked skyward and wondered about the we sicken, how we heal—educated guesses, traditions, and farthest edges of our solar system. Some people preferred religious faiths explained all of these natural phenomena. Pluto to the ringed beauty of Saturn or the galactic girth No rigorous way existed to test new ideas about our world. of Jupiter. The man who discovered Pluto went from a Then stargazers started to notice that heavenly objects small-town hero to a national legend nearly overnight. didn’t behave the way tradition said they should. In the Pluto, the smallest of planets, became a loveable symbol early 1500s, Polish astronomer for any underdog. proposed an idea that shook the world. He suggested that Then in 2006, astronomers stripped Pluto of its the Earth and all the other planets revolve around the sun, “planet” status and labeled it a “dwarf planet”— instead of the other way around. Many refused to accept whatever that was. Pluto’s 76-year run as a planet Copernicus’ ideas. was over. A century later, Italian astronomer Galilei The story of Pluto is about how things change. revisited Copernicus’ ideas, this time with the help of Specifically, it’s about how things change in light of more advanced telescopes. By observing the movement new evidence. Pluto’s story is a story about science. of planets, Galileo proved Copernicus’ theory correct.

37 Brontosaurus Planetary scientist Veronica Bray worked on a NASA team that learned more about Pluto from a flyby. THE NAME GAME Nicknamed “the thunder lizard,” the Galileo’s work is an early example of the scientific Brontosaurus was one of the largest animals to ever walk the Earth. Then one day the method in action. “These observations turned Copernicus’ Brontosaurus just vanished. This wasn’t hypothesis into a proven theory,” says Veronica Bray, another extinction. This time around, a planetary scientist at the University of Arizona and Brontosaurus fell victim to a naming glitch. part of the NASA team responsible for the Scientific tradition dictates that when a spacecraft that flew past Pluto in 2015. “It shows that no new organism is discovered or identified, matter how unpopular a result, scientists will update their it’s assigned a two-word Latin name. For opinions in light of newly discovered information.” example, Homo sapiens is the fancy name for The scientific method provides a framework to subject a human. This naming device is called the new ideas to rigorous testing. Using this method, scientists Linnaean System, named for its originator, the test and improve their ideas, called hypotheses or theories, eighteenth-century naturalist Carl Linnaeus. by performing experiments or making observations. Brontosaurus is a genus, or group of closely related species, first identified in 1879. A similar Only after passing these tests can ideas become accepted genus called Apatosaurus was identified two scientific knowledge. years earlier. Most important to Pluto’s story, the method calls for During the 1900s, paleontologists reviewing scientists to re-examine old ideas in light of new evidence. the evidence concluded that Apatosaurus and This evidence might arise from a fresh discovery or a Brontosaurus are actually the same genus. Since technological innovation. The scientific method provides scientists named Apatosaurus first, Linnaean a tool to question everything that we assume to be true . . . rules say the giant beast must be called even the number of planets in our solar system. Apatosaurus. Uh oh. The news hit Bronto fans like a giant meteor. The Search for Planet X In 2015, an exhaustive study re-examined By the twentieth century, astronomy had come a long way similarities between Brontosaurus and Apatosaurus. The results showed enough since the days of Copernicus. Advances in telescopes and differences between the two dinosaurs other technologies led to discoveries of distant moons to separate them on the family tree. So and comets and other space bodies. But scientists had Brontosaurus is back—for now. observed only eight planets. Some astronomers were —Charles C. Hofer convinced that another planet lay beyond . This mysterious planet became known as Planet X. In 1930, while working in the in Flagstaff, Arizona, young astronomer tested some planet-hunting techniques. By applying some new tweaks to old methods, he shed light on the darkest corners of our solar system. Before long, Tombaugh discovered Planet X! An 11-year-old in England named suggested calling the planet “Pluto.” The world celebrated. Our solar system was complete. However, even as Pluto gained recognition as a planet, doubt began to arise. Here’s why: the planets in our solar system fall into two main categories. First, there are the Apatosaurus 38 Pluto’s oblong orbit doesn’t match the orbits of other planets.

terrestrial planets of Mercury, , Earth, and . clear “NO.” The IAU voted to change Pluto’s status. And These planets are small and solid, made of rock and that was the end of Pluto as the ninth planet. ice. They are close to the sun. Then there are gas giants, represented by Jupiter, Saturn, , and Neptune. The End? These planets are massive, ringed, and composed mainly Of course, an entire planet can’t just vanish. The IAU of gas. While the terrestrial planets and the gas giants are demoted Pluto to a “dwarf planet,” a new classification very different from each other, all planets clearly fall into that includes Eris and fellow Kuiper Belt dwellers. The one category or the other. Pluto, however, does not. world reacted in dismay. After all, for many, tiny Pluto Naysayers argued that tiny Pluto didn’t deserve planet had become the favorite planet. But science isn’t a status. Pluto was too much of an oddball. Others argued popularity contest. that the little celestial body had enough characteristics “Pluto was the first Kuiper Belt object discovered,” that other “official” planets possessed. Astronomers says Bray. “Over time, more and more Kuiper Belt debated back and forth about the true of Pluto. objects were discovered. We realized we’d had it wrong all along.” New evidence about the Kuiper Belt allowed The “No’s” Have It scientists to re-examine what they thought they knew It all began to unravel for Pluto in 2005. The Kuiper Belt, about our solar system. As a result, they updated how an area at the edge of our own solar system, is home to they classify planets. For Pluto, the rules of the game countless space rocks, large and small, including Pluto. had changed. Many astronomers believe the Kuiper Belt is made “Once you get to see the variety of worlds that are up of debris that drifted away when our solar system out there, you realize that it doesn’t matter what it’s was formed. called,” says Bray. “Pluto is still as cool and complex Astronomer Mike Brown of the California Institute of as it ever was!” Technology was convinced that rocks the size of Pluto— Science keeps moving forward. Today’s scientists and perhaps even larger—exist in the Kuiper Belt. In are asking questions that the next generation will 2005, he finally found one. It’s called Eris. answer. And you never know. With new scientists Now that Pluto was considered one large object in applying fresh ideas, the story of a possible ninth the Kuiper Belt, among others, its days as a planet were planet is far from finished. numbered. At the annual meeting of the International Astronomer’s Union (IAU) a year later, astronomers Charles C. Hofer is a biologist living in Arizona, where he waits present held a vote. Is Pluto a planet? The answer was a patiently for the IAU to reconsider its decision about Pluto.

39 by Stephanie M. Bucklin M Dis

OSIRIS-REX WILL INVESTIGATE ONE SPECIAL ASTEROID.

s you read this, an asteroid almost a third But to get this right, scientists have to ensure that of a mile (one-half kilometer) in diameter everything about this seven-year mission goes smoothly. is hurtling toward Earth. And a spacecraft First up: a navigation maneuver near Earth. Ais hurtling toward that asteroid. It’s all part of a mission to take a Final Rendezvous with Earth sample of that asteroid and return it to Earth. Scientists In late September 2017, the spacecraft, called say this sample could offer us important clues about how OSIRIS-REx, will pass by the Earth for the final time. (Its our planet developed—and how life formed here. full name is Origins Spectral Interpretation Resource

40 A

In September 2017, the spacecraft OSIRIS-REx will use Earth’s Mission gravity to launch itself toward an asteroid called Bennu.

“Think about a toy airplane on the end of a string,” Knutson says. “You’re holding it, and as you turn in a circle, that airplane is kind of pulling away from you and keeping the string taut. It’s the same kind of thing.” The spacecraft will use our planet’s gravity to power it in the right direction—just as, if you released that airplane at the right to moment, it would go flying away in the chosen direction. An Asteroid Like an Egyptian God The mission centers on Bennu, an asteroid named in 2013 by North Carolina third-grader Michael Puzio. Michael entered an international contest. He suggested “Bennu” because he thought the spacecraft that will be traveling to the asteroid, OSIRIS-REx, resembles pictures of the Discover ancient Egyptian god Bennu. The god is often depicted as a gray heron. But why this asteroid? Currently, Bennu is orbiting the sun (just like the planets do). But there’s a slight chance—1 in 2,500—that Bennu could hit the Earth in the late twenty- second century. If heat from the sun, reflected away from the asteroid, changes Bennu’s orbit enough, it may point toward Earth. But this potential danger is not the only reason NASA Our scientists selected Bennu for this important mission. They picked Bennu out of over half a million other asteroids when searching for the perfect one to take a sample from. Bennu stood out for a couple of reasons. The asteroid had to be relatively close to the Earth, about 150 million miles (240 million km) away or less. (As a comparison, the distance between the Earth and the sun Past is about 93 million miles or 150 million km.) Next, the asteroid had to have the right orbit—one similar Identification and Security-Regolith Explorer. No wonder it in shape to Earth’s. The goes by a nickname.) asteroid also had to be The reason for the rendezvous? OSIRIS-REx will essentially over 656 feet (200 m) use the pull of Earth’s gravity to “slingshot” into a new in diameter. Smaller trajectory towards the asteroid, according to Sara Knutson, asteroids spin so rapidly science operations engineer at the University of Arizona and that the spacecraft would an OSIRIS-REx team member. The navigation maneuver is have trouble collecting a called the “Earth Flyby” or “Earth Gravity Assist” (EGA). sample from it.

Egyptian god Bennu 41 The rocket carrying NASA’s OSIRIS-REx spacecraft lifted off on September 8, 2016.

In August 2018, OSIRIS-REx will fire rockets and then slow down to make sure it meets up with Bennu.

Finally, scientists wanted to select the most primitive type of asteroid, meaning one that is carbon-rich and hasn’t changed much since its formation about 4 billion years ago. For almost a year, the spacecraft will use instruments to measure and map the asteroid. These asteroids contain important molecules that may offer scientists insights about early life on Earth. With these specifications, scientists narrowed the number of asteroids from more than 500,000 to just 5. Out of these, they picked Bennu as the lucky winner. The Extraction OSIRIS-REx is slated to arrive at the asteroid Bennu in the summer of 2018. There, the spacecraft will perform the most important maneuver of its journey: the extraction of a sample. It won’t be easy. OSIRIS-REx will first have to map the asteroid to understand its shape and to select the best sample site possible. Scientists will choose the site with care. In fact, they will spend two years planning the sample grab. Primarily, In July 2020, OSIRIS-REx will “kiss” the surface of Bennu to retrieve they’ll be looking for a safe place to approach, Knutson says—a a sample. part of the asteroid that is relatively flat, with few boulders

In March 2021, engines will fire to put OSIRIS-REx on course back This mechanical arm will touch the asteroid Bennu. to Earth. We’re expecting to see it again in 2023.

42 A NASA illustration shows the spacecraft’s sampling arm making contact with Bennu’s surface.

Prior to launch, a team hoisted OSIRIS-REx in the air. or other large obstacles, where OSIRIS-REx’s sample collector will be able to extract a decent number of grains (particles of material) from the asteroid. Ideally, that means 60 grams— about the weight of a Baby Ruth candy bar—or more. But the spacecraft won’t land on the asteroid. Instead, it will “kiss” the surface, using the precious up-close moments to blast out gas that shakes up the grains on Bennu. Then the spacecraft will capture and store those grains for the journey home to Earth. Homeward Bound After the sample collection, OSIRIS-REx will begin its journey back to Earth. Four hours before reaching the , the spacecraft will release its sample Asteroids: Bringers and return capsule (SRC). The capsule will parachute down to Destroyers of Life the Earth’s surface at the Utah Test and Training Range, What can the dirt from this asteroid tell us about life? outside of Salt Lake City. The anticipated arrival date is To answer this, it’s first important to understand just September 24, 2023. how asteroids impacted life on Earth. You may be familiar Crews won’t waste any time: once the SRC has with the theory that asteroids wiped out the dinosaurs, but landed, they’ll prepare the sample and transport it to asteroid impacts don’t just destroy life—they may have the Johnson Space Center. There, researchers will helped bring it to Earth originally. open the sample canister and examine the sample, Sankar Chatterjee, professor of geosciences at Texas creating a detailed inventory in preparation for more Tech University, says that asteroids “contain the missing in-depth analysis. chapter of the early history of our planet.” About 4 billion Six months after the SRC lands, NASA will begin to years ago, when the Earth was young, asteroids and comets distribute this sample to research groups around the began to pummel the planet’s surface. This period is often world who submitted proposals to NASA about the work called the . “To me,” Chatterjee they’d like to do. But an amazing 75 percent of the sample says, “asteroid impacts are like the cosmic dance of Hindu will not be used. It will be set aside for future generations god Shiva, which causes renewal and death.” Sure, they did of scientists, who will be able to use equipment not yet damage, but scientists theorize that these asteroids may invented to test ideas not even yet thought of. have also brought the building blocks of life.

43 Incoming! This image is a NASA artist’s concept of OSIRIS-REx approaching Bennu.

Say “Yellow cheese!” These instruments are part of OSIRIS-REx’s Camera Suite.

NASA scientists and staffers keep the media up to date on the OSIRIS-REx mission.

An Ongoing Mission Seven years may seem like a long time for a mission, but researchers have such big plans for the sample upon its return that they don’t mind waiting. “This project is really special,” Knutson says. She So what are those building blocks? They include explains that hundreds of college students will contribute carbon and water. Scientists believe that asteroids similar over the course of the mission. “Students were involved in to Bennu brought both to Earth during the Late Heavy designing, building, and testing parts of the spacecraft and its Bombardment, Knutson says. Because Bennu likely has instruments,” she says. “They’re also involved in navigation not changed much over its billions of years of existence, and mission planning. Now that we’ve launched, students are the molecules we find on its surface will give us good clues analyzing data and looking at images, and in 2023, they will about what types of materials those early asteroids brought help examine the sample.” to Earth. Knowing this may help scientists piece together Will you be a college student in 2023? You may have a the story of the elements that led to life on Earth. chance to take part in this important mission examining For instance, amino acids, tiny components of life forms, the role of “deadly” asteroids in forming life on Earth. can have one of two orientations: what scientists call “left- handed” and “right-handed.” Amino acids on Earth are almost Stephanie Bucklin writes middle-grade fiction and science articles. always left-handed. Scientists studying the sample from Bennu She has not yet visited any asteroids, though she is quite grateful to could check whether any amino acids they find are right- NASA’s robots for taking on this mission. She can only imagine that handed or left-handed. If all amino acids are left-handed, it with all the photographing and surface kissing, the meeting might get might help explain why that orientation rules on Earth. a little awkward.

44 BY IVARS PETERSON

TRAPPIST-1 is an ultra-cool dwarf star orbited by seven Earth-sized planets. astronomers had to conclude they were looking at more than one planet!

Math Suppose a star has two planets, one completing an orbit every 20 days and the

the other every 50 days. How often would you see the star grow fainter over a period of 100

Do days? What would tell you there have to be two planets? To get additional data, NASA’s Spitzer Space Telescope measured TRAPPIST-1’s brightness nearly continuously for 20 days, capturing 34 crossings (also called transits) of planets in front of the star. Sorting through the mess of data, the astronomers found that the innermost planet completes its orbit in 1.5 Earth days, while the outermost planet takes 20 days. PLANET SEARCH Once you know how long it takes each planet to complete Math helps us chart the were the size of a basketball, an orbit, you can work out universe. TRAPPIST-1 would be the size how far it is from the star of a golf ball. This star is one of compared with the other our closest neighbors, about planets. For example, start 235 trillion miles (378 trillion with a planet that takes twice On a clear night, away from city km, or 40 light-years) away as long as another planet to lights, you can see a sky packed from Earth. orbit. Multiply the distance with stars. But you can’t see When astronomers using by itself (2 x 2 = 4), then find planets orbiting any of these Earth-based telescopes what number multiplied by stars, even with the strongest studied TRAPPIST-1, they itself three times gives you the Earth-based telescopes. noticed that every once in same answer. In this case, the Planets are smaller than stars a while, it became slightly answer is roughly 1.59 times and don’t give off their own fainter. They decided that a farther away. The final step is light to make them visible. planet must be passing in called finding the cube root of Astronomers reported the front of the star, blocking part a number. discovery of seven Earth-sized of the light. This dimming The TRAPPIST-1 planets are planets orbiting a nearby star would come and go as the not alone. So far, astronomers called TRAPPIST-1 in February planet orbited the star, passing have identified more than

2017. They had to rely on alternately behind and in front 3,400 planets (known as text © 2017 by Ivars Peterson indirect evidence to tell them of the star at regular intervals. exoplanets) that orbit other that the planets are there. By By making careful stars. Observing changes of doing some math, they figured observations, astronomers brightness is just one of a range out the number of planets and expected to get a rough idea of tools they have used to build the distance of their orbits. of the planet’s size from the up this catalog. Whatever the TRAPPIST-1 is a red dwarf pattern of dimming light. method, math is a key part of star, just a fraction of the size But the light level dipped making the invisible visible— of our own sun and only a bit often and not at evenly and expanding our universe larger than Jupiter. If the sun spaced times. The MUSE NEWS of known planets. FALSE STORY Solar Flair 45 CONTEST

Inventor ANNOUNCING toNEW the CONTEST CONTEST WINNERS! I look around me Stars In February 2017, the songs At the waves hitting the beach Imagine of eco-activist Xiuhtezcatl Soon, all this won’t be you’re a future Martinez inspired us. We astronomer. You asked readers for poems or ANISYA M. / age 12 / California want to get a better lyrics about protecting the environ- view of exciting events ment. Bravo to everyone who sent and elements in our solar their work! These winners really hit POACHED system. Maybe the goal is to high notes. develop a new tool for safely A wild disruption, viewing a solar eclipse. Or A fear eruption. perhaps you want high-def You heard it cry, images of asteroids. Design an invention that will help You watched it die. you see a space object in a THE FUTURE A tiger’s death, whole new way. Use words, Its final breath. diagrams, or even a photo of I look into the future a model to share the and I can see two dusty paths; You hunt them, it’s what you do, invention with us. Remember one leading to destruction, You’re a poacher, that part’s true too. to explain how it works and what it will help you study. the other to where life lasts. ETHAN J. / age 12 / Illinois Happy inventing! I look into the future CONTEST RULES 1. Your contest entry must be and I see a beach your very own original work. where no beach should be Ideas and words should not and beautiful creatures be copied. once endangered, now extinct, 2. Be sure to include your name, age, and full address and the air stinks on your entry. of smoke 3. Only one entry per person, and smog please. and fog 4. If you want your work returned, enclose a self- and Thailand’s curse. addressed, stamped We survive, envelope. but do we, 5. All entries must be signed by a parent or legal as a species, guardian, saying that this do we thrive? is your own work and no help was given and granting permission to publish. For I look into the future, detailed information about and I see a beach our compliance with the Children’s Online Privacy where a beach should be, Protection Act, visit the and formerly endangered species policy page at cricketmedia live and breathe .com/privacy. TISHYA J. / age 10 / Washington 6. Your entry must be and you can breathe received by August 31, 2017. an atmosphere clean We will publish winning entries in the January 2018 and drink water crystal clear. issue of Muse. We survive. RUNNERS-UP

7. Send entries to Muse We ALL thrive. Honorable Mention Contest, 70 E. Lake St., Suite This month’s runners up are 800, Chicago, IL 60601 or via Kari P., age 12, Minnesota; email to muse@cricketmedia. Which future would YOU like? Maggie H., age 11, Nebraska; com. If entering a digital Zoe Z., age 8; Annabel T., age 9, photo or scan, please send at SAMANTHA N. / age 14 / Virginia 300 dpi. New York; and Hinke Y., age 11, 46 Virginia. BY KATHRYN HULICK MATTHEW BILLINGTON Tech

Your

SHOULD HUMANS WORRY study it further. Jason Kessler of ABOUT KILLER ASTEROIDS? NASA says that the program will allow “more people to play a role AN ASTEROID impact likely wiped out the dinosaurs. Could in protecting our planet.” another one obliterate humanity? The risk of a large asteroid But is it really worth worrying slamming into Earth during your lifetime is relatively low. You about something that has such have an estimated 1 in 75 million chance of dying in such a a low chance of happening? Phil catastrophe. A fireworks accident (1 in 50 million), a bee sting Plait writes a blog called Bad (1 in 25 million), or a lightning strike (1 in 10 million) is more Astronomy, where he debunks If only there’d likely to take you out. been an app science myths. Asteroids are one Despite the long odds, astronomers and scientists keep an for that. of his favorite things to write eye on the sky for nearby objects that might pose a threat. Now, about—he even sports a tattoo thanks to technology, you can join them. of a fireball slamming into Earth. The free AsteroidTracker app for iOS and Android keeps He says: “Asteroid impacts are you up to date with news about all known objects from space something I’m concerned about, that will pass near Earth. You can also follow @AsteroidWatch but not something I’m worried or @lowflyingrocks on Twitter for updates. If you happen to about. I think about them, and have a backyard telescope that can take pictures of the sky, you work toward getting people can scout out new asteroids yourself using a free computer to understand them, but they program called Asteroid Data Hunter. don’t keep me awake at night in To develop the software, NASA partnered with Planetary terror, sweating and staring at Resources, Inc., a company that aims to mine asteroids for the ceiling.” resources. The program compares multiple images of the Do you worry about an same spot in the sky, looking for any lights that have moved. asteroid strike? Would you These could be asteroids. The program then tries to match any download an app or computer suspicious lights to known asteroids. If it can’t make a match, program to help keep an eye on it directs the user to report the object to astronomers who will the sky?

47 BY NANCY KANGAS GREG KLETSEL Slice Last

THE MISSING DEFINITIONS (Ĭ-KLĬPS’)

e•clipse 1. verb. To cut in front of someone in line and pretend you haven’t done anything wrong

2. noun. An eclair presented as part of an apology

3. verb, slang. To accomplish a task effortlessly without preparation

4. somewhat improper noun. A small noise that sounds like a person passing gas but is really something else E•clipse 1. proper noun. Online barber school popular from 2015 to 2016 e•clipse•y 1. adj ective. Overbearing, bossy text © 2017 by Nancy Kangas 48 Carve out some time to read COBBLESTONE.

We’re doing monumental things with U.S. history.

Discover American History Nagel Photography/Shutterstock.com Nagel

FOR SALE T H LOUISIANA E PURCHASE Subscribe at Shop.CricketMedia.com/Try-Cobblestone July/August 2017 Volume 21 Number 06 cricketmedia.com $4.95

To be outdoors as the universe around you darkens, with the light turning eerie . . . is the most remarkable experience.Ó