SCIENTISTS DISCOVER PLANET ORBITING STAR.

Byline: Bill Dietrich The Seattle Times

New instruments at an old observatory have detected a Jupiter-size planet orbiting a star only 8.1 light years from Earth - the closest star yet to have its own world.

The discovery around the small red star Lalande 21185 follows recent findings of planets around three sunlike stars in the greatest rush of new worlds since Columbus stumbled upon the Western Hemisphere.

Announcement of the discovery came Tuesday at a meeting of the American Astronomical Society.

The new planet appears to be orbiting the star at a distance about as far as Saturn is from our sun, with the period of the orbit from 30 to 35 years and a mass somewhat smaller than Jupiter - the giant of our solar system.

There is also intriguing evidence of a smaller, second planet orbiting the star every six years at a distance 2-1/2 times as far as Earth is from the sun, or about where the asteroid belt is in our own solar system. And the star's motion is so complex, it may even suggest a third planet.

Astronomers are not yet able to detect Earth-size planets, however, and most of the new worlds found to date appear unlikely to support life as we know it.

Discovery of the newest planet was announced by astronomer George Gatewood of the University of Pittsburgh's Allegheny Observatory.

Gatewood used two tactics. One was to take photographic plates of the star dating back to 1930 and remeasure motion of Lalande 21185 using new instruments. The other involved the use, beginning in 1988, of a new, 30-inch lens to view the star, coupled with photoelectric detectors.

The two methods confirmed that Lalande 21185 speeds up and slows down as it circles the core of the Milky Way galaxy, responding to the pull of a giant planet orbiting around it.

An alien civilization viewing our sun from afar would see it similarly speed up and slow down from the tug of Jupiter and other planets, and, given accurate enough measurements, could infer our solar system has several planets.

Not only is the new planet circling a nearby star, it is also about the same distance from Lalande 21185 as our giant planets are from the sun, suggesting our solar system may not be unusual. That could be important in determining how many stars might have Earth-like rocky planets at the right distance from the sun.

Detecting Earth-size planets and using their light spectrum to detect the presence of water or oxygen is not possible using existing telescopes because the planets are lost in the glare of our sun and that of their home stars.

University of Arizona astronomer Roger Angel has proposed building a new space telescope at approximately the orbit of Jupiter, far enough away from our sun's light to see faint planets more clearly. Angel said the technology to do so exists today.

Actually visiting a star such as Lalande 21185 is still impractical for existing or currently possible spaceships, which would take centuries or millennia to travel even 8.1 light years. A light year is the distance light travels in a vacuum in one year.