National Aeronautics and Space Administration The Helix Nebula: What is it?

The object shown on the front of this poster is the This “Mountains Helix Nebula. Although this object and others like it are of Creation” image called planetary nebulae (pronounced NEB-u-lee), they was captured by really have nothing to do with planets. They got their name the Spitzer Space ZKHQDVWURQRPHUV¿rst saw them through early telescopes, Telescope in infrared because they looked similar to planets with rings around light. It reveals them, like Saturn. billowing mountains of dust ablaze with A planetary nebula is the ¿res of active star really a shell of glowing gas formation. GALEX and plasma from a star at the can see the new stars end of its life. The star has forming, because they glow brightly in ultraviolet (UV) light. blown off much of its material However, the surrounding dust and gas clouds are cooler and and what is left is a very not so visible to GALEX. compact object called a white dwarf. For a while, the white dwarf is still hot and bright A Tug of War enough to make the material Planetary nebula JnEr1, A star is an amazing from the former star glow, as seen by GALEX. ! Ow! If not for balancing act between two ! * * gravity, my head and that is what we see as a * * would explode! beautiful nebula. Over 10,000 huge forces. On the one * years or so, the gas will drift away and the white dwarf will hand, the crushing force of the star’s own gravity Gravity Heat cool so much that we can no longer see the nebula. Gravity tries to squeeze the stellar Pressure This is what will happen to our Sun in about 5 billion material into the smallest years. What do you suppose our Sun’s nebula will look and tightest ball possible. like to some distant alien astronomers? But on the other hand, the force of the tremendous To understand what res burning at the star’s happens to a star at the end KHDWDQGSUHVVXUHIURPWKHQXFOHDU¿ center tries to push all that material outward. of its life, we need to know something about the rest of a When the star has used up almost all of its hydrogen star’s life, from birth, through nuclear fuel (after several billion years), the outward middle-age (our Sun’s stage pressure from the nuclear reactions is no longer able to of life now), and into its last counteract the gravity, and the core of the star collapses stage of life. under its own weight, so to speak. As the core collapses, it gets even hotter. The outer layers of the star puff up from Planetary nebula A21, as this increased heat, but as the star puffs up, the outer layers seen by GALEX. get cooler. The star is called a red giant at this point. Our own Sun will become a red giant before it dies in How Does a Star Form? about 5 billion years. It will be so large at this stage in its Stars are born where there are thick clouds of gas life that it will engulf the orbits of Mercury and Venus and (mostly hydrogen) and dust in space. Gravitational maybe even Earth. Even if Earth remains outside the Sun, attraction makes these materials clump together. The the oceans and the atmosphere will have boiled away and “clumped” object grows more and more massive as more nothing will be able to live on what will be a burnt cinder and more gas gets pulled in by the growing gravitational of rock. force. As the object becomes more massive, squeezed by But even as the outer layers puff up, the core of a red tremendous gravitational forces, it becomes more dense giant continues to contract and get even hotter. When the (compact). As it gets denser, it gets hotter and hotter. FRUHJHWVKRWHQRXJKWKHQXFOHDU¿res are once again lit, as Eventually, if the giant gas ball gets massive enough and the helium atoms fuse into carbon and oxygen atoms. It dense enough, the atoms of hydrogen gas will begin to is in the cores of dying stars that much of the carbon and fuse together, creating helium atoms and igniting the oxygen atoms in ours bodies were made! QXFOHDU¿res that make it a star.

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National Aeronautics and Space Administration Clues from Ancient Light

This activity introduces some important The same thing happens to starlight. The galaxies science concepts in simple language. The puzzle are all moving away from us and each other because space itself is expanding. As the light waves move through activity reinforces one aspect. Participants cut out expanding space, they get stretched out. The longer the the squares on the second page with the pictures light waves’ journey through space, the more stretched out of objects of different “ages,” then rearrange they become. Astronomers say this stretched out light is them from oldest to youngest. A third page shows “red-shifted.” the pictures in the right order (allowing room for differing interpretation in a couple of cases), How Old Is the Starlight? explaining a little about each picture. If desired, the puzzle page may be photocopied and glued to GALEX sees starlight that has been traveling for just card stock or a manila folder before cutting out the a few years from stars that are “only” a few tens of trillions squares. of kilometers away. But it also sees really stretched out “red-shifted” starlight that has been traveling over 10 billion years! That is more than two-thirds of the age of the whole universe! So GALEX is seeing faraway galaxies GALEX Looks Back in Time as they were a very long time ago when they gave off the light, as well as nearby galaxies as they looked just a few Like all telescopes that see far into space, GALEX hundred thousand years ago. is a time machine. As it peers into the distance, it is also peering into the past. That is because the light that GALEX Just as old photographs show how people looked detects has taken a long time to travel from its source (a decades ago, GALEX sees pictures of galaxies when the galaxy, for example) to reach GALEX. Although light universe was much younger than now. So astronomers travels faster than anything else (300,000 kilometers or can look at the galaxy pictures from far away—and long 186,000 miles per second, in round numbers), it does not ago—compare them with pictures of galaxies nearby—very WUDYHOLQ¿nitely fast. That means, while light travels, time recent—and see how galaxies and their stars are born, age, passes. The farther it travels, the more time passes. and die over time. They can learn how galaxies evolve. The distance light can travel in one Earth year is called a light year. A light year is a very long distance: How Old Do I Look? around 9 trillion kilometers (6 trillion miles). Can you tell how old something is just by looking at it? The squares on the next page contain pictures of Light travels in waves, similar to the way water waves old things, new things, and every age in between things. move through the ocean or sound waves move through Cut out the squares. For each row (A – F) of six pictures the air1H[WWLPHD¿re truck approaches with its siren from a single category, like nature or animals, arrange the blasting, listen closely. You will notice that the siren’s note objects by age, oldest on the left, youngest on the right. deepens a little just as the truck passes you. The note is Some things may be a little hard to compare, but make a lower because the sound waves are being stretched as the good guess anyway. At least be able to explain why your truck continues to move away from you. arrangement by age could be right! Compare your best guesses to ours on the answer page.

light wave

Space expanding STAR EARTH over time stretches light waves traveling through it. Light travels in waves, just as energy traveling through the ocean pushes the water into waves. But as light waves travel through space, they gradually get stretched out. That is because, along with the universe, space itself is expanding and stretching the distances between things.

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CUT OUT SQUARES. IN EACH ROW, ARRANGE OLDEST TO NEWEST (LEFT TO RIGHT).

A: Nature A: Nature A: Nature A: Nature A: Nature A: Nature

Earth Tree Galaxy Bee hive Mountain Flower B: Animals/ B: Animals B: Animals B: Animals B: Animals B: Animals

Baby Butterfly Milk cow Old man Giant tortoise Baby bird C: Transportation C: Transportation C: Transportation C: Transportation C: Transportation C: Transportation

Pegasus rocket Wright (launched GALEX brothers’ Volkswagen space telescope) Covered wagon First metal bike Viking ship airplane Beetle D: Communication D: Communication D: Communication D: Communication D: Communication D: Communication

Telephone Telephone Telephone (separate ear & (combined ear & GALEX ground (rotary dial) Cell phone mouth pieces) mouth pieces) station antenna Smoke signals E: Gone quickly E: Gone quickly E: Gone quickly E: Gone quickly E: Gone quickly E: Gone quickly

Birthday candle Cloud Soap bubble flame Flower Lightning Leaf F: “Imagers” F: “Imagers” F: “Imagers” F: “Imagers” F: “Imagers” F: “Imagers”

GALEX space Isaac Newton’s 35-millimeter telescope Box camera Telescope film camera Digital camera Cave painting

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ANSWERS! A A A A A A

Mountains can be This galaxy, M81, Trees can be This beehive is almost as old as is over 10 billion hundreds of years likely to be at least This daffodil looks Earth itself. Some years old. Picture old. This one looks a few days old. It very fresh, Earth is about 4-1/2 are just a few taken by the at least a few years could be older than probably just a day billion years old. million years old. GALEX telescope. old. the tree though! or two old. B B B B B B

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 calf before they can crawling, so he is years! This one This man looks of their life cycle. still in his shell. It give milk. They are probably between may not be that old, about 80 or 90 This phase usually may be only a few usually at least two six months and one but it might be over lasts only about one minutes old. years old. year old. 100. years old. week. C C C C C C

The Pegasus rocket This ship might Covered wagons The first all-metal Wright brothers’ The last was first launched have been used by were used by the bicycle appeared in airplane flew Volkswagen Beetle from a big airplane the Viking warriors settlers of the 1870. Covered successfully in “love bug” was in 1990. It more than 1000 western U.S. during wagons were still in 1903. made in 1978. launched GALEX years ago. the 1800s. use though! in 2003. D D D D D D

This later model Native Americans has a rotary dial. This cell phone is “talked” by smoke This kind of This kind of rotary The ear and mouth one of the newest GALEX ground signals long before telephone phone appeared in pieces can be held models. May be stations in Hawaii Europeans arrived appeared during the thelate1950s. newer than in one hand. and Australia began in the 1600s. early 1900s. GALEX ground antenna. operating in 2002. E E E E E E

This dandelion Howoldisacloud? This leaf (if it is This candle is very Up to 18 lightning doesn’t last long Clouds are always A bubble floating still on the tree) small so the flame bolts can strike in before it turns to a changing. But in the air is fragile could be several will burn for only a one second, so this puff of fuzzy seeds maybe it will look and usually pops in days or weeks old. thesametoyoufor couple of minutes. one must be very that blow away. a few seconds. a few minutes. young indeed! F F F F F F

This “look through Digital cameras GALEX space 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 from over 15,000 reflecting telescope in the 1950s. than the box photography. First advanced imaging years ago. in 1672. camera. sold in the 1990s. instruments.

EW-2006-07-026-JPL 5 National Aeronautics and Space Administration GALEX: The Galaxy Evolution Explorer

GALEX (short for Galaxy billions of years to reach us from the galaxies that were its Evolution Explorer) is a space source. telescope orbiting Earth since 2003. GALEX observes *$/(;LVHVSHFLDOO\JRRGDW¿nding star galaxies in ultraviolet (UV) nurseries—places where new stars are forming inside light. Because Earth’s galaxies. GALEX can see these hot, baby stars well, atmosphere blocks most UV because they shine brightly in ultraviolet light. And light, GALEX must be above because GALEX does not see visible light, it is not the atmosphere. confused by the larger number of older stars. By studying galaxies near and far away, especially those that glow GALEX is looking at tens strongly in ultraviolet, scientists can understand better of millions of galaxies spanning where and how stars are formed, how galaxies come to be, much of the universe. A galaxy and how galaxies change over cosmic time. is a grouping of stars, gas, dust, planets, moons, and various strange objects such as black holes all held together by gravity. All but a few stars in the universe live in galaxies. Our Sun is just one of at least 200 billion stars in our own Milky Way Galaxy. The entire universe probably contains over 100 billion galaxies. Stars, planets, galaxies, clouds of dust and gas, and other matter in space are sending out energy all the time. This energy, called electromagnetic energy, travels in waves. Like waves traveling through the ocean, electromagnetic waves can be very long, very short, or The beautiful Andromeda Galaxy (or M31) is the nearest anything in between. large galaxy to our own Milky Way Galaxy. On the left is Therefore, the light we see from the Sun and other Andromeda as it appears through a visible light telescope stars—the visible light—tells only a small part of the story (at a bit smaller scale). The image on the right was of the stars. To get the complete picture, we must extend made by GALEX, capturing Andromeda’s UV light. The our vision to include other wavelengths or energies of star-forming regions in the spiral arms are quite clumpy light. That is why scientists and engineers have invented compared to the vast regions of old stars. (Visible light different kinds of telescopes. For example, we have special image courtesy of John Gleason.) telescopes for the long radio waves; special telescopes for GALEX can detect stars and galaxies that are about the infrared waves that we cannot see but rather feel as 40 million times fainter than ones we can see with our heat; and we have special telescopes such as GALEX for unaided eyes from even the darkest skies here on Earth. detecting invisible ultraviolet waves. *$/(;LVWKH¿rst mission to map most of the sky in UV GALEX detects the UV light coming from nearly light at a great enough distance to survey galaxies outside the farthest parts of the universe. Some of this light is our own galaxy. Its all-sky map will also help astronomers almost two-thirds as old as the universe itself, having taken ¿nd the most interesting looking galaxies for future study in detail using other telescopes.

Radio MicrowaveInfrared Visible Ultraviolet X-ray Gamma Ray 4 2 -2 -5 -6 -8 -10 -12 1010 110 10 10 10 10 10 Wavelength in centimeters

About the size of...

Buildings Humans Bumble Bee Pinhead Protozoans Molecules Atoms Atomic Nuclei

This material was contributed by the Jet Propulsion Laboratory, California Institute of Technology, reÀ ecting research carried out under a contract with the National Aeronautics and Space Administration. EW-2006-07-026-JPL 6