National Aeronautics and Space Administration GALEX Galaxy Evolution Explorer

This object, called Jupiter’s Ghost or NGC 3242, is a planetary nebula. In this image, taken in ultraviolet light by the Galaxy Evolution Explorer (GALEX), Jupiter’s Ghost appears far larger than it does in visible light. This cloud of gas and debris, glowing in the ultraviolet light from the hot white dwarf star at the center, is all that is left of a star that was once similar to our Sun. The ghostly remains from a star’s violent death

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EW-2009-12-042-JPL Jupiter’s Ghost: What is it? The Sun as a red giant SunThe Sunnow Now Clues from Ancient Light The object shown on the front of this poster is This “Mountains (5 billion years from now) The same thing happens to starlight. The galaxies of Creation” image This activity introduces some important Ghost,” because seen through an ordinary telescope in are all moving away from us and each other because space was captured by science concepts in simple language. The puzzle visible light, it does somewhat resemble the planet Jupiter. itself is expanding. As the light waves move through the Spitzer Space activity reinforces one aspect. Participants cut out But even though this object and others like it are called Sun now Mercury Venus Earth expanding space, they get stretched out. The longer the Telescope in infrared the squares on the second page with the pictures planetary nebulae (pronounced NEB-u-lee), they really light waves’ journey through space, the more stretched out light. It reveals have nothing to do with planets. They got their name of objects of different “ages,” then rearrange they become. Astronomers say this stretched out light is billowing mountains them from oldest to youngest. A third page shows The SunSun as as a aWhite white Dwarf dwarf “red-shifted.” of dust ablaze with (6 billion years from Now) because they had a disk-like (6 billion years from now) the pictures in the right order (allowing room appearance similar to planets. for differing interpretation in a couple of cases), How Old Is the Starlight? formation. GALEX explaining a little about each picture. If desired, can see the new stars A planetary nebula is In 5 billion years or so, the Sun will puff up and become a Eventually (after its red giant phase), the Sun will become the puzzle page may be photocopied and glued to GALEX sees starlight that has been traveling for just forming, because they glow brightly in ultraviolet (UV) really a shell of glowing gas red giant star, swallowing up Mercury and Venus. In this a white dwarf, about the same size as Earth, but hundreds card stock or a manila folder before cutting out the a few years from stars that are “only” a few tens of trillions light. However, the surrounding dust and gas clouds are and plasma from a star at the picture, the orbits of Mercury, Venus, and Earth compared of thousands of times more dense. The Sun’s diameter as of kilometers away. But it also sees really stretched out cooler and not so visible to GALEX. squares. end of its life. The star has to the size of the Sun as a red giant are to scale, but the a white dwarf will actually be about 110 times smaller “red-shifted” starlight that has been traveling over 10 blown off much of its material sizes of the planets and of the Sun now are not to scale. than it is now. billion years! That is more than two-thirds of the age of and what is left is a very A Tug of War The Sun’s diameter as a red giant will be about 80 times the whole universe! So GALEX is seeing faraway galaxies compact object called a white larger than it is now. as they were a very long time ago when they gave off the Planetary nebula JnEr1, GALEX Looks Back in Time dwarf. For a while, the white A star is an light, as well as nearby galaxies as they looked just a few as seen by GALEX. ! Ow! If not for The image of Jupiter’s Ghost on the front of the Like all telescopes that see far into space, GALEX dwarf is still hot and bright amazing balancing ! * * gravity, my head A Fight to the Finish hundred thousand years ago. * * would explode! poster is from the Galaxy Evolution Explorer. The is a time machine. As it peers into the distance, it is also enough to make the material act between two huge * from the former star glow, and that is what we see as a forces. On the one The nuclear reactions that are creating carbon and extended region around the planetary nebula shows in peering into the past. That is because the light that GALEX Just as old photographs show how people looked oxygen once again exert outward pressure and stop the dramatic detail in this image, induced by the white dwarf detects has taken a long time to travel from its source (a decades ago, GALEX sees pictures of galaxies when the beautiful nebula. Over 10,000 years or so, the gas will drift hand, the crushing Gravity Heat Gravity away and the white dwarf will cool so much that we can no force of the star’s own Pressure collapse of the core. But this time, the nuclear reactions to glow with ultraviolet light. Jupiter’s Ghost is about galaxy, for example) to reach GALEX. Although light universe was much younger than now. So astronomers longer see the nebula. gravity tries to squeeze are very sensitive to temperature. If the temperature goes 1,400 light-years away in the constellation Hydra. travels faster than anything else (300,000 kilometers or can look at the galaxy pictures from far away—and long the stellar material up just a little, the nuclear reactions happen a lot faster, 186,000 miles per second, in round numbers), it does not ago—compare them with pictures of galaxies nearby—very This is what will happen into the smallest and releasing a lot more energy, making the temperature go up Learn More About Galaxies, Ultraviolet travel infi nitely fast. That means, while light travels, time recent—and see how galaxies and their stars are born, age, to our Sun in about 5 billion tightest ball possible. even more. The star becomes very unstable. It begins to passes. The farther it travels, the more time passes. and die over time. They can learn how galaxies evolve. years. What do you suppose pulsate violently, as the gravitational and nuclear forces Light, and Nebulae But on the other hand, the force of the tremendous heat and The distance light can travel in one Earth year is our Sun’s nebula will look GALEX Website, http://www.galex.caltech.edu. See How Old Do I Look? called a light year. A light year is a very long distance: like to some distant alien into space. “Image Gallery.” tries to push all that material outward. around 9 trillion kilometers (6 trillion miles). astronomers? Hubble Space Telescope Gallery of Planetary Nebula Can you tell how old something is just by looking When the star has used up almost all of its hydrogen As the gases are blown off, they form a cloud around at it? The squares on the next page contain pictures of To understand what Images: http://hubblesite.org/newscenter/newsdesk/ Light travels in waves, similar to the way water waves nuclear fuel (after several billion years), the outward what is left of the star. As more of the star’s atmosphere old things, new things, and every age in between things. happens to a star at the end archive/releases/category/nebula/planetary. move through the ocean or sound waves move through pressure from the nuclear reactions is no longer able to blows away, deeper and hotter layers of the star’s core are Cut out the squares. For each row (A – F) of six pictures of its life, we need to know The Space Place, http://spaceplace.nasa.gov. Under the air. Next time a fi re truck approaches with its siren counteract the gravity, and the core of the star collapses exposed. Finally, the surface of what is left of the star is so from a single category, like nature or animals, arrange the Planetary nebula A21, as something about the rest of a “Projects,” see “Galactic Mobile” and “Galaxy blasting, listen closely. You will notice that the siren’s note under its own weight, so to speak. As the core collapses, it hot that it makes the cloud of gases around it glow. That objects by age, oldest on the left, youngest on the right. seen by GALEX. star’s life, from birth, through Montage” activities. Under “Games,” see “How old deepens a little just as the truck passes you. The note is gets even hotter. The outer layers of the star puff up from glowing cloud of gas is what we call a planetary nebula. Some things may be a little hard to compare, but make a middle-age (our Sun’s stage of life now), and into its last do I look?” lower because the sound waves are being stretched as the this increased heat, but as the star puffs up, the outer layers good guess anyway. At least be able to explain why your stage of life. What is left behind at the center is called a white Universe by Robin Kerrod, DK EYEWITNESS BOOKS, truck continues to move away from you. get cooler. The star is called a red giant at this point. dwarf, made mostly of carbon and oxygen. It will 1st ed. (March 2003), ISBN: 0789492385 (ages arrangement by age could be right! Compare your best guesses to ours on the answer page. How Does a Star Form? Our own Sun will become a red giant before it dies in eventually cool off and become more and more dense, 9-12). about 5 billion years. It will be so large at this stage in its because there are no more nuclear reactions pushing Galaxies by Seymour Simon, Harper Trophy, Reprint ed., Stars are born where there are thick clouds of gas life that it will engulf the orbits of Mercury and Venus and outward to counterbalance the gravitational forces that pull 1991, ISBN: 0688109926 (ages 9-12) light wave (mostly hydrogen) and dust in space. Gravitational maybe even Earth. Even if Earth remains outside the Sun, inward. Finally, the white dwarf may have half the mass Our Galaxy and the Universe by Ken Gruan et al., Ken attraction makes these materials clump together. The the oceans and the atmosphere will have boiled away and of the Sun contained in an object with the volume of Earth. Press, 2002, ISBN: 1928771084 (ages 9-12). “clumped” object grows more and more massive as more (Today the Sun has a volume more than one million times nothing will be able to live on what will be a burnt cinder Light, by David Burne. 1st ed., 2000, DK Publishing Space expanding and more gas gets pulled in by the growing gravitational of rock. that of Earth!) (DK Eyewitness Books). ISBN: 0789467097, ages STAR EARTH force. As the object becomes more massive, squeezed by 9-12. over time stretches light waves The white dwarf will eventually cool off so much that tremendous gravitational forces, it becomes more dense But even as the outer layers puff up, the core of a red Invisible Universe: The Electromagnetic Spectrum from traveling through it. it will no longer illuminate the gases of the nebula. We are (compact). As it gets denser, it gets hotter and hotter. giant continues to contract and get even hotter. When the Radio Waves to Gamma Rays : Grades 6-8, by Alan lucky to see planetary nebulae at all because they glow for Eventually, if the giant gas ball gets massive enough and Gould and Stephen Pompea. Published by LHS Light travels in waves, just as energy traveling through the ocean pushes the water into waves. But only a few tens of thousands of years, compared with the dense enough, the atoms of hydrogen gas will begin to the helium atoms fuse into carbon and oxygen atoms. It GEMS; Teacher edition (August 1, 2002). ISBN: as light waves travel through space, they gradually get stretched out. That is because, along with the lifetime of a typical star, which can be several billion years. fuse together, creating helium atoms and igniting the is in the cores of dying stars that much of the carbon and 0924886692. universe, space itself is expanding and stretching the distances between things. oxygen atoms in ours bodies were made.

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Pages 4 and 5 may be downloaded at http://spaceplace.nasa.gov/en/kids/galex/whats-older.pdf GALEX: The Galaxy Evolution Explorer

GALEX (short for Galaxy GALEX is especially good at fi nding star CUT OUT SQUARES. IN EACH ROW, ARRANGE OLDEST TO NEWEST (LEFT TO RIGHT). nurseries—places where new stars are forming inside ANSWERS! Evolution Explorer) is a space telescope orbiting Earth since galaxies. GALEX can see these hot, baby stars well, A: Nature A: Nature A: Nature A: Nature A: Nature A: Nature A A A A A A 2003. GALEX observes because they shine brightly in ultraviolet light. And galaxies in ultraviolet (UV) because GALEX does not see visible light, it is not light. Because Earth’s confused by the larger number of older stars. By studying Mountains can be This galaxy, M81, Trees can be This beehive is galaxies near and far away, especially those that glow almost as old as atmosphere blocks most UV is over 10 billion hundreds of years likely to be at least This daffodil looks strongly in ultraviolet, scientists can understand better years old. Picture Earth itself. Some old. This one looks very fresh, light, GALEX must be above Earth is about 4-1/2 a few days old. It where and how stars are formed, how galaxies come to be, taken by the are just a few at least a few years probably just a day the atmosphere. billion years old. could be older than Earth Tree Galaxy Bee hive Mountain Flower GALEX telescope. million years old. old. or two old. and how galaxies change over cosmic time. the tree though! GALEX is looking at tens B: Animals/ B: Animals B: Animals B: Animals B: Animals B: Animals B B B B B B of millions of galaxies spanning much of the universe. A galaxy is a grouping of stars, gas, dust, planets, moons, and various Giant tortoises can Butterflies we see This little chick has Cows must bear a This baby is live from 150-200 are in the last part just hatched and is strange objects such as black holes all held together by calf before they can crawling, so he is years! This one This man looks of their life cycle. still in his shell. It gravity. All but a few stars in the universe live in galaxies. give milk. They are probably between may not be that old, about 80 or 90 This phase usually may be only a few Our Sun is just one of at least 200 billion stars in our own usually at least two six months and one but it might be over lasts only about one minutes old. years old. year old. Milky Way Galaxy. The entire universe probably contains Baby Butterfly Milk cow Old man Giant tortoise Baby bird 100. years old. week. over 100 billion galaxies. C: Transportation C: Transportation C: Transportation C: Transportation C: Transportation C: Transportation C C C C C C Stars, planets, galaxies, clouds of dust and gas, and other matter in space are sending out energy all the time. The Pegasus rocket The beautiful Andromeda Galaxy (or M31) is the nearest This ship might Covered wagons The first all-metal Wright brothers’ The last was first launched This energy, called electromagnetic energy, travels have been used by were used by the bicycle appeared in large galaxy to our own Milky Way Galaxy. On the left is airplane flew Volkswagen Beetle from a big airplane in waves. Like waves traveling through the ocean, Wright the Viking warriors settlers of the 1870. Covered Andromeda as it appears through a visible light telescope successfully in “love bug” was in 1990. It Pegasus rocket more than 1000 western U.S. during wagons were still in electromagnetic waves can be very long, very short, or (at a bit smaller scale). The image on the right was (launched GALEX brothers’ Volkswagen 1903. made in 1978. launched GALEX years ago. the 1800s. use though! anything in between. space telescope) Covered wagon First metal bike Viking ship airplane Beetle in 2003. made by GALEX, capturing Andromeda’s UV light. The star-forming regions in the spiral arms are quite clumpy D: Communication D: Communication D: Communication D: Communication D: Communication D: Communication D D D D D D Therefore, the light we see from the Sun and other stars—the visible light—tells only a small part of the story compared to the vast regions of old stars. (Visible light of the stars. To get the complete picture, we must extend image courtesy of John Gleason.) This later model Native Americans our vision to include other wavelengths or energies of This kind of has a rotary dial. This kind of rotary This cell phone is GALEX can detect stars and galaxies that are about “talked” by smoke one of the newest GALEX ground light. That is why scientists and engineers have invented telephone The ear and mouth phone appeared in signals long before models. May be stations in Hawaii 40 million times fainter than ones we can see with our Telephone Telephone appeared during the pieces can be held the late 1950s. different kinds of telescopes. For example, we have special Europeans arrived newer than and Australia began unaided eyes from even the darkest skies here on Earth. Telephone (separate ear & (combined ear & GALEX ground early 1900s. in one hand. GALEX ground telescopes for the long radio waves; special telescopes for in the 1600s. operating in 2002. GALEX is the fi rst mission to map most of the sky in UV (rotary dial) Cell phone mouth pieces) mouth pieces) station antenna Smoke signals antenna. the infrared waves that we cannot see but rather feel as E E E E E E light at a great enough distance to survey galaxies outside E: Gone quickly E: Gone quickly E: Gone quickly E: Gone quickly E: Gone quickly E: Gone quickly heat; and we have special telescopes such as GALEX for our own galaxy. Its all-sky map will also help astronomers detecting invisible ultraviolet waves. fi nd the most interesting looking galaxies for future study This dandelion How old is a cloud? GALEX detects the UV light coming from nearly in detail using other telescopes. This leaf (if it is This candle is very Up to 18 lightning doesn’t last long Clouds are always A bubble floating the farthest parts of the universe. Some of this light is still on the tree) small so the flame bolts can strike in before it turns to a changing. But in the air is fragile The GALEX mission is managed by the Jet could be several will burn for only a one second, so this almost two-thirds as old as the universe itself, having taken puff of fuzzy seeds maybe it will look and usually pops in Propulsion Laboratory and the California Institute of Birthday candle days or weeks old. the same to you for couple of minutes. one must be very billions of years to reach us from the galaxies that were its that blow away. a few seconds. Technology. Cloud Soap bubble flame Flower Lightning Leaf a few minutes. young indeed! source. F F F F F F F: “Imagers” F: “Imagers” F: “Imagers” F: “Imagers” F: “Imagers” F: “Imagers” Radio MicrowaveInfrared Visible Ultraviolet X-ray Gamma Ray 4 2 -2 -5 -6 -8 -10 -12 1010 110 10 10 10 10 10 This “look through Digital cameras GALEX space Wavelength in centimeters Isaac Newton This box camera the lens” camera is like this are the telescope, launched Cave paintings date designed the first was probably made most likely newer latest advance in in 2003, has very About the size of... from over 15,000 reflecting telescope in the 1950s. than the box photography. First advanced imaging GALEX space Isaac Newton’s 35-millimeter years ago. in 1672. camera. sold in the 1990s. instruments. telescope Box camera Telescope film camera Digital camera Cave painting Buildings Humans Bumble Bee Pinhead Protozoans Molecules Atoms Atomic Nuclei This material was contributed by the Jet Propulsion Laboratory, California Institute of Technology, refl ecting research carried out under a contract with the National Aeronautics and Space Administration. EW-2009-12-042-JPL 4 EW-2009-12-042-JPL 5 EW-2009-12-042-JPL 6