PAGE: 1 PAGE: 2 Table of Contents LEXILE® MEASURE 3 Copernicus, King of Craters 870L 4 Catching Andromeda’s Light 890L 6 Merry Christmas from the Moon! 810L ©Highlights for Children, Inc. This item is permitted to be used by a teacher or educator free of charge for classroom use by printing or photocopying one copy for each student in the class. Highlights® Fun with a Purpose® ISBN 978-1-62091-227-0 PAGE: 32 object—either a rocky asteroid or an icy comet—was more than a mile in diameter. Still, there are larger craters on the Moon, so why is Copernicus special? The answer is simple: because the crater faces Earth directly, it looks nice and round, exactly the way everyone thinks a crater should look. But what really makes Coper- nicus special is its halo of rays. These wispy streamers stretch outward in every direction. Like the crater itself, they are brightest when the Moon is full. Take a close look at these feather-like Copernicus splashes. When a big object blasts out a crater, the smallest particles travel farthest from the point of impact. This spray of rock then falls in a splash pattern onto the lunar surface. This material looks bright because it’s made up of crushed and broken rock, which Copernicus, King of Craters By Edmund A. Fortier On the Moon, this crater rules. The best-known impact crater on to the left of the Moon’s center. reflects light better than the dust- Earth is Meteor Crater. It is You’ll see a small bright spot covered lava plain. nearly a mile across and about 550 against the gray. That’s Over long periods of time, feet deep. To see it, you would have Copernicus. the constant bombardment by to drive far out into the desert in Since the Moon doesn’t have an meteoroids darkens the rays and Arizona. atmosphere to protect it as Earth mixes them with the surface dust. The Moon’s best-known meteor has, tiny grains of space debris Eventually the rays disappear. crater is Copernicus. It is 58 miles called meteoroids collide with the Copernicus’s rays are still bright in diameter and more than 2 miles Moon constantly. This meteoroid because this crater is young. It’s from top to bottom. To see “rain” wears down the lunar only 810 million (810,000,000) it, you just have to step outside surface, creating a layer of dust. years old. Many other large and look at the Moon through Meteoroids the size of rocks and craters are nearly 4 billion binoculars. boulders strike the Moon less (4,000,000,000) years old. You may have already noticed often, but they are more powerful. The crater is named after that the Moon’s surface is a mix of These rocks can produce craters the great astronomer Nicolaus bright and gray areas. The gray measuring anywhere from a few Copernicus. In the 1800s, another areas are lava plains. The largest feet to several miles across. On astronomer studied this scar on and darkest lava plains are found rare occasions, the Moon is hit by the Moon’s surface. He called it along the left-hand side of the an object the size of the one that “the Monarch of the Moon.” Today, Moon. Using binoculars, look just carved out Copernicus. That we can call it the king of craters. ©Highlights for Children, Inc. This item is permitted to be used by a teacher or educator free of charge for classroom use by printing or photocopying one copy for each student in the class. Highlights® Fun with a Purpose® Photo courtesy of NASA ISBN 978-1-62091-119-8 PAGE: 32 Catching Andromeda’s By Ken Croswell, Ph.D. Photo by Robert Gendler Light The Andromeda Galaxy is the closest giant galaxy to our own. By observing Andromeda, astronomers have learned a lot M32 about our Galaxy, the Milky Way. A Spiral Galaxy Spiral arms In 1887, Isaac Roberts, an astronomer in Wales, discovered that Andromeda is a Andromeda’s spiral arms arise because the galaxy is spinning. AppearingGiant above and spiral galaxy—the most below Andromeda are two smaller galaxies, which are orbiting around it. beautiful type. He black hole made his discovery by photographing the galaxy. Unlike the eye, photographs A galaxy is a can collect dim light huge collection for hours. Then they of stars, gas, show faint things and dust that that the eye can’t are held close to Andromeda’s spiral see. one another by arms, he thought they What about the might also trace the Milky Way Galaxy? gravity. Milky Way’s spiral The stars of Andromeda People wondered arms. So in 1951, even reveal how far away the whether it was a spiral, too. But Morgan mapped the locations of galaxy is. It works like this. they couldn’t tell. We live in the all the red clouds of gas he and Astronomers observe a type Milky Way, so we can’t see it from his colleagues could find. He of star in Andromeda. Then the outside. discovered that the gas clouds they compare the star with the Astronomers counted the lined up along spiral arms, same type of star in the Milky Milky Way’s stars in different indicating that we live in a spiral Way. The fainter the star in directions. They hoped to see a galaxy. Andromeda looks, the farther spiral pattern. But they didn’t Why do red clouds of gas trace away Andromeda must be. succeed. the spiral arms? It’s because It’s like seeing a distant Fortunately, the Andromeda spiral arms give birth to stars. streetlight. By comparing its Galaxy helped. Walter Baade, The brightest newborn stars faintness with the streetlight an astronomer in America, took are hot and blue, so spiral arms in front of your home, you can a photograph that showed red are blue. The blue stars give off estimate how far the distant clouds of gas that lined up with ultraviolet radiation—light waves streetlight is. Andromeda’s spiral arms. that are shorter than your eye can Andromeda is 2.5 million Another astronomer in see. This ultraviolet light carries (2,500,000) light-years away. America, William Morgan, saw lots of energy and makes gas glow One light-year is a long way: that photograph and had an idea. red. So, strangely enough, gas can it’s the distance light travels Since red clouds of gas trace turn red when it’s near blue stars. in a year, about 5.88 trillion ©Highlights for Children, Inc. This item is permitted to be used by a teacher or educator free of charge for classroom use by printing or photocopying one copy for each student in the class. Highlights® Fun with a Purpose® ISBN 978-1-62091-118-1 PAGE: 33 larger than M32, is called NGC 205. Big Black Holes Andromeda and the Milky Way have even more in common. Each Spiral arm galaxy has a giant black hole at its center. A black hole is an object with so much mass and gravity that nothing can escape it—not even light, the fastest thing in the universe. Astronomers discovered Andromeda’s black hole after they saw that the stars and gas near NGC 205 the galaxy’s center move fast. Why so fast? The Earth moves fast around the Sun. But if the Sun had much more mass than it does, the Earth would move much faster. So the very high speed of the The giant galaxy stars and gas near Andromeda’s center means there must be next door is a lot miles from Earth. so much mass that it’s a black The Andromeda Galaxy is like ours. hole! Astronomers calculate that Andromeda’s central black hole has 140 million times more mass than the Sun. The black hole at the center of 15,000,000,000,000,000,000 the Milky Way is smaller—only 4 million times the mass of the Sun. Just as the Earth goes around the Sun, the Sun goes around the Milky Way’s big black hole. (5,880,000,000,000) miles. Galactic Empires But don’t worry: the black hole is So the Andromeda Galaxy Both Andromeda and the Milky 27,000 light-years away. Plus, the is about 15 quintillion Way are giant spiral galaxies. Sun moves half a million miles per (15,000,000,000,000,000,000) miles Each galaxy is so large that many hour—so fast that it won’t fall into from Earth. other galaxies go around it, just the black hole. All other stars in Believe it or not, that’s not as the Moon goes around the Earth. the Milky Way also move around very far—at least, as galaxies We call these smaller galaxies the black hole at the Galaxy’s go. Andromeda is so close that “satellite galaxies,” for center. it is part of the Local Group of the same reason we call the Moon Likewise, all the stars in the galaxies. a satellite of the Earth. Andromeda Galaxy move around The Local Group has dozens The photograph here shows two its central black hole. Perhaps of galaxies. Andromeda is the of Andromeda’s satellite galaxies. some of those stars have planets brightest one in the Local Group. The round one that appears above with intelligent beings who have Our Galaxy, the Milky Way, ranks Andromeda’s disk is called M32. learned a lot about their galaxy— number two.