Tools of the Astronomer

The earliest people studied the stars with just their naked eyes. Our eyes detect light, and the light forms images on our retinas, the center part of our eyes. Today we can study the universe with everything from binoculars to super strong telescopes.

When Galileo turned the first telescope toward the skies, he was able to see wonderous things - craters on the Moon, dark spots on the surface of the Sun, tiny moons moving aroung Jupiter. No one else had ever seen these things. With modern telescopes we are able to see many more things.

A telescope is like a small bucket. Light from planets, stars and galaxies "rains down" on Earth, and a telescope collects this light and lets us look at the object the light came from.Some telescopes, called refracting telescopes, collect and focus light through a glass lens. Another type, the refleting telescopes, reflect light on a glass mirror. The bigger the telescope the more light it collects, giving us a better view of what we want to look at. TheKeck Telescope in Hawaii is the world's largest optical telescope. It doesn't have just one big mirror, it has 36 little mirrors that fit together like bathroom tile. With the help of a computer, these little mirrors work together like one big 10 meter mirror.The Hubble Space Telescope is the largest orbiting optical telescope in history. Arecibo radio telescope is the largest single-dish telescope in the world right now.

The refracting and reflecting telescopes collect and focus visible light, which is light that we can see. There are also other types of light that we cannot see. Astronomers have built many different types of telescopes to look at all the different types of light. On Earth we can look at visible light and radio waves. Some of the very largest telescopes are radio telescopes, like the VLA in New Mexico. Other types of light, like X-ray light and ultraviolet light, can only be looked at from space, so astronomers have built telescopes in space that orbit the Earth. The most famous is the Hubbell Space Telescope.

With the aid of these tools, we have learned so much more about our Universe than we could have just studying the night sky with our eyes.