ASTRONOMERS FIND 4TH PLANET OUTSIDE EARTH'S SOLAR SYSTEM.

Byline: Associated Press 

A team of San Francisco State University astronomers have found a planet beyond Earth's solar system, the fourth in six months.

The astronomers made their find after having surveyed about 100 stars located about 30 light years from Earth. The latest planet has a mass about 80 percent as large as Jupiter and is 9 million miles from its star, HR3522. It travels around its star every 14.76 days.

``We have found four planets, and that's 4 percent,'' professor Geoffrey Marcy said.

``So I would say that 4 percent of all stars have planets at least as large as Earth. What we don't know is the frequency of planets like Earth. But I would tend to speculate that Earth-like planets are extremely common,'' Marcy said.

In searching for planets, the astronomers analyze the spectrum of light from stars to detect any slight, cyclical motions, which are considered responses to the gravitational pulls of orbiting planets.

Marcy, his co-discoverer Paul Butler and a group of students will continue their search in July in Hawaii at the Keck Observatory, home to the world's largest telescope.

The recent finds are creating a golden age for scientists who for years have been frustrated by not being able to find planets despite the abundance of stars, said University of California at Santa Cruz astronomer Douglas Lin.

``Now, remarkably, we are starting to be able to study planets as a group of objects, not just a few individuals around the sun,'' Lin said.

But scientists still can't figure out why the planets, most likely formed away from their stars, have spiraled in.