e Stars th g n S EA R C H LIG H T Which of these things do astronomers study stars planets moons astronauts comets Stud y i 6
ASTRONOMY DID YOU KNOW ight takes about eight minutes to les from the Sunl l l travel the 93 mi Sun to the Earth ion mi Look at the sky What do you see If it’s day you’ll see the Sun If it’s night you’ll see the Moon And if the sky is clear you’ll see stars In big cities you may see only a few hundred stars But out in the country or on the ocean you’ll see many thousands You may even see planets and if you’re lucky a comet There are people who look at the sky for hours and hours night after night They study the stars the planets and other objects in the sky These people are called astronomers The word astronomy comes from the Greek for star and arrangement Astronomers study the universe in many different ways Some watch faraway objects Others work in laboratories where they look at samples of meteorites rocks from the Moon and space debris from other planets Some try to make models of different objects people have studied Not all astronomers get paid for the work they do Some do it for a hobby Such people are called amateur astronomers How do astronomers study objects that are millions even billions of miles away They use powerful telescopes that make things look large enough to be seen in detail Some telescopes are small enough to be held in the hand Others are as big as a school bus LEARN MORE READ THESE ARTICLES COPERNICUS SOLAR SYSTEM UNIVERSE Answer They study all of these except for astronauts 7
I n finiteSpace The universe is a vast expanse of space that contains all matter and energy from the smallest particle to the biggest galaxy It contains all the planets the Sun stars asteroids our Milky Way Galaxy and all the other galaxies too No one knows how big the universe is Astronomers believe that it is still growing outward in every direction How did it all begin No one knows that for sure either Most scientists believe that at first everything was one incredibly solid heavy ball of matter This ball exploded billions of years ago and the universe was born The moment of this explosion is called the big bang It is from this moment that time began After the explosion the early universe was small and extremely hot As it cooled it expanded and pieces spread out Small pieces formed the basic S EA R C H LIG H T If the universe is still growing is it moving toward or away from the Earth 8
UNIVERSE elements hydrogen and helium Other pieces began to join together and objects began to form Over billions of years the objects became galaxies stars and planets This is still only a theory an idea But different parts of it have proved true over the years Astronomers try to investigate the theory all the time One way they do this is to use a spectroscope A spectroscope measures the color of light coming from an object Changes in the color indicate whether an object is moving away from or toward the Earth Because of spectroscope readings scientists believe that the universe is still growing outward in every direction LEARN MORE READ THESE ARTICLES GALAXIES SOLAR SYSTEM STARS D I D YO U K N O W ieve that much of the universe may be made of something Scientists bel l e d d a r k m a t t e r T h i s h i d d e n mass may be a substance that human cal beings have never before encountered balloon blow it up and watch the dots spread apart thing else You can see how this works if you put black dots on a Answer Everything in the universe is moving away from every 9
