New eyes to scan the skies.

Four hundred years ago, an Italian scientist named Galileo Galilei became the first person to see the craters on the moon. Galileo, who also observed four of Jupiter's moons and the rings of Saturn, was one of the first people to use a telescope to study the sky. Since then, telescopes have become the most important tool used by astronomers.

All over the world--from the mountains of Hawaii to the icy plains of Antarctica--astronomers use telescopes to study the stars, galaxies and planets of outer space. Today, telescopes come in all shapes and sizes. Scientists are constantly finding new ways to make these instruments more powerful. In the next couple years, two new telescopes with different purposes are scheduled to see "first light." (This is the phrase used by astronomers to talk about the first images produced by a telescope.)

[ILLUSTRATION OMITTED]

One of the telescopes, called Pan-STARRS, could save humans from extinction. Nick Kaiser, a scientist who works on the project, says the Pan-STARRS telescope has been designed to find "90 percent of all killer asteroids, near-Earth asteroids bigger than 300 meters." Smaller asteroids often crash into Earth, but if a giant "killer" asteroid were to strike our planet, it could mean the end of human civilization.

Pan-STARRS, like most telescopes, uses mirrors and lenses to provide pictures of outer space. Giant mirrors are used to "gather" light. They reflect the light onto the lens of a camera, which can then record the image.

When completed, Pan-STARRS will include four telescopes perched atop a mountain on the Hawaiian island of Maui. Only one telescope is in place and working now. Each telescope will take pictures of one patch of sky for about 30 seconds, and then move on to another patch. Every night, each telescope will take pictures of about 1,000 patches. Every week, each telescope will have photographed the whole sky.

Each of the four telescopes will take pictures of the same patches of sky. One telescope, working alone, may occasionally malfunction and incorrectly detect an asteroid. If there are three other telescopes working, astronomers can use them to see if there really is an asteroid coming our way. By using four telescopes instead of one, scientists hope to get a more accurate picture of space. If a giant asteroid were identified, astronomers would plot ways to deflect it or break it up long before it reached Earth.