World Book at NASA for Students
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Astronomy is the study of the stars, planets, and other heavenly bodies. Astronomers try to find out where these heavenly bodies are and how they move. They study what planets are made of. They learn about how stars create their light. They make theories, or guesses, about how and when the universe formed.
Image to right: In this drawing, a spacecraft traveling toward Saturn releases a probe. The probe will fall to one of Saturn's moons to study it. Credit: NASA
Astronomy is one of the oldest sciences. It began in ancient times. Back then, people first noticed that the heavenly bodies move in cycles, or repeated patterns. Ancient astronomers believed that the sun and planets traveled around the Earth. But in 1543, a Polish astronomer named Nicolaus Copernicus said that the Earth and other planets traveled around the sun. Astronomers of the past knew only about the objects they could see with their naked eye or with small handheld telescopes.
Today, astronomers use many instruments, or tools, to study the universe. Huge telescopes give astronomers close-up views of space objects. These telescopes help astronomers study objects that are fairly close to the Earth, such as the sun, the planets, and comets. To learn about objects farther away, radio telescopes pick up the energy given off by space objects. Other instruments allow astronomers to study the light given off by space objects. Computers help astronomers make sense of the information they get from all these instruments.
How to cite this article: To cite this article, World Book recommends the following format: "Astronomy." The World Book Student Discovery Encyclopedia. Chicago: World Book, Inc., 2005.
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