Everything Kids' Astronomy Book (7 page)
Seeing Double?
Have you ever had a tug of war with your friends? Algol is often called the “demon star” because it is hidden at times by its aging companion star. It almost seems to be playing hide and seek with you. This red giant seems to be losing gas to its brighter twin because of their close orbits! A tug of war between twin stars is not that unusual, and sometimes the winner is not who you would expect it to be. A companion star is often found only by the effect it has on another star. One way to spot them is if they wobble from the pull of the unseen star's gravity. Could the other star be a black hole? When you go to the planetarium, you might ask if they have to use two projectors to show these binary or “twin” stars. Maybe they will show videos of the real ones!
Try This
Star Parties
Who doesn't want to be a star? For this party all you need are a few costumes, some sunglasses, a star cake, and a camera. Roll out the red carpet and have a few friends come over for some star trivia, treats, and pictures. Everyone should make a star with their name on it for their own door at home.
Which One?
I can make things disappear
and reappear simply
by doing what I always do.
Which one am I?
A. Eclipse
B. Supernova
C. Rocket
D. Comet
Naming Your Own Star
The first time you meet someone new, you learn the person's name. Stargazers like Ptolemy started naming the stars in the sky thousands of years ago to help identify and keep track of them. You might be surprised to know that many of the names the stars are called today came from Middle Eastern astronomers living thousands of years ago. Unfortunately the same star was known by a different name in other places in the world. Modern astronomers started adding Greek letters to the unnamed stars in the newly discovered constellations like some of those in the Southern Hemisphere. They would name the brightest star Alpha, the next would be Beta, and so on until they ran out of stars or letters! This is not a foolproof way to know which are the brightest stars though, because the astronomers didn't want to change their names even after they found out the stars weren't quite as bright as earlier astronomers thought they were.
Some countries have tried naming newly discovered stars after their celebrities, but as you probably have noticed, there aren't any famous names listed on the star maps. Some astronomers have been honored for their discoveries by having their names used, but the newer stars just have initials that indicate the type of star they are, or numbers, or both. Now, when a star is found it is simply listed by its coordinates on the celestial sphere. If you want to find a new star, looking at catalogs that list the stars may help you. If you look closely, you may see the same star listed with its different names and numbers. Some day you might find a star that no one else has ever found before.
Try This
It's All Greek to Me!
How about trying something new like learning the Greek alphabet, which is used for many things besides naming stars? You can find it in an encyclopedia or on the Internet by typing in the words “Greek alphabet.” Are there any other alphabets you would like to learn? How about the sign language alphabet?
Across the Sky
The word list is here to give you a hand, but be carefulâ there are two extra words!
ACROSS
6. A picture seen ir a pattern of stars
8. Collections of stars, gas, and dust held together by gravity. The Milky Way is one!
11. Huge balls of gas that produce light anc heat. Our sun is one!
12. The Earth's shadow across the moon
13. Two stars in orbit around each other (2 words)
DOWN
1. "Shooting Stars"
2. A small, icy ball with a iong, glowing tail
3. The galaxy that hods dut solar systen (2 words)
4. An exploding star
5. When the whole face of the moon is lit up (2 words)
7. The large spheres that orbit around our sun. Sone lave rings!
9. A powerful explosion on the sun (2 words)
10. A small rocky object that ortr'ts the sun
FUN FACT
Second Look
Beginning astronomers occasionally think they have found twin stars, until they look at them through a larger telescope, only to find the second star is not even close to the other star!
The First Star I See Tonight!
Does it seem like there are a lot of faint stars when you look up at the sky? One reason this is true is because bright stars don't last very long. Usually a white dwarf star is one that has used up all its fuel. If this star is “running out of gas,” how could it possibly become a nova that lights up the sky like fireworks and then go dim again? This happens because a nova has a companion star that pours its gas around the white dwarf until the surface of the dwarf star is burning again. Once the fuel is gone, so is the light. This second life can happen only once or it might happen many times, so keep an eye on the sky to see if you spot one! Would you think that a nova could be the brightest star in the sky? Many of the brightest stars are found in the constellations of the zodiac. Castor and Pollux are the two bright stars found in the well-known constellation of the Gemini twins. Another bright star is Aldebaran, which seems to form the eye of Taurus the bull. See if you can find Regulus, the bright star located at the base of Leo the lion's tail. There are several bright stars in the super bright constellation called Pleiades that are also known as the seven sisters. They would all be good places to look for the brightest star near us, but we don't have to travel very far or consult a star map in your newspaper to find the winner. If you guessed the brightest star close to Earth is the sun, you're right. Most people forget that the sun is a star. From here, the sun is very bright, but if you wanted to look at the sun from another galaxy, you would need a very strong telescope to see it! See how many people you can fool when you ask them the question, “Do stars only come out at night?” If they say, “Yes,” ask them, “What about the sun?”
Just for Fun
What's Your Sign?
Do you know what your sign is according to the dates in astrology? If you are born near the beginning of the year, you may be an Aquarius or a Capricorn. If you were born in the summer you may fall under the sign of Cancer or Gemini. There are twelve signs in the zodiac all based on constellations.
Happy Birthday to You
How would you like to see a bunch of baby stars? Many astronomers say that one of the “stars” in the belt of the constellation Orion is a nebula filled with protostars, which is the last step before a star is born or becomes a true star! For a star to survive, the pressure from the burning fuel pushing outward must equal the gravity pulling inward. Have you ever flown in a hot air balloon? The heat of the fire forces the balloon up while gravity tries to pull the balloon back to the ground. Although a star like the sun is not very big during the middle of its life, it is much, much larger when it is forming and while it is dying. Do you think the star's pressure change is what causes this to happen? If you said yes, you're right!
Orion has two giant stars in its constellation, a blue giant called Rigel and a red giant called Betelguese (pronounced beetle juice). Neither will have a long life as far as stars go. Huge stars like Rigel burn hotter and faster than a small star, so this red giant's hydrogen is almost gone and it is starting to burn its core. The original size of a giant star will determine if it will burn to a cinder or explode into a supernova when it reaches the iron core. Scientists believe the explosions are caused when the iron puts out the fire that was keeping up the pressure inside the star's core. Eventually gravity crushes it, then all of the contents, some too small to be seen, come rushing out.
Mapping the Stars
Have you ever watched an airport beacon's light sweeping through the air? Their beacons use many different combinations of colors and rotating speeds of light to indicate what type of airport it is. Astronomers found a new type of variable star in the constellation Cepheus that pulsates like these beacons, which helps to tell them what type of star it is. A Cepheid is a star that is unstable because it is slowly dying. Its temperature, size, and radiation are causing its brightness to change at a regular rate, but the rate or period of brightness is not the same for every star. Once astronomers learn a star is in a Cepheid stage and how long its pulsation period is, they can calculate how far away it is. This is just one more way of measuring the immense distances to the stars. Other methods are:
Found out in Space
Look carefully at this letter grid through your telescope. How many of the deep space objects from the word list can you find? Answers can go side to side, or up and down.
FUN FACT
Sun or Star?
Any star the same size of Earth's sun or smaller is considered to be a dwarf star. The sun is known as a yellow dwarf star.
1. Using radar within the solar system.
2. Calculating increasing distances using geometry.
3. Comparing the brightness of different stars.
4. Figuring out the speed of rotating galaxies.
5. Photographing the explosions of the supernovae.
Just for Fun
Pie in the Sky
How about a sky you can eat? All you need is a paper plate covered in whipped cream. Add a drop or two of blue food coloring and stir it with a spoon. To make your stars in the sky you can add marshmallows, candy pieces, cookie crumbs, or star shaped pieces of flavored gelatin. Then eat.
Because of all of this, in less than a century astronomers have progressed from believing that the sun was the center of the universe to learning that the universe extends for somewhere close to 13 billion light years. If you remember each light year is about 6 trillion miles, how many total miles is that? Will your calculator handle that many numbers?
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Appendix A
Glossary
alien
Beings thought to live somewhere else out in space are called aliens. No one is sure if there is any other life in the universe, other than here on Earth. Another name for an alien is an extraterrestrial.
asteroid
An asteroid is a small object similar in several ways to a planet. Many asteroids are made of rock and orbit the sun.
astrology
A belief that stars and other objects in space can be used to predict future happenings or events.
People who are born under certain signs are expected to have certain characteristics and qualities.
astronaut
Explorers who travel out into space are known as astronauts. Some astronauts have become famous for taking the first steps in space or being the first woman or man to leave the Earth's atmosphere.
astronomy
The study of all things in space. The people who watch the skies for new stars or planets or changes in the ones that have already been discovered are called astronomers. Astronomy is a type of science.