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'Rebel' Stars Move in Sun's Neighborhood

Posted on: Wednesday, 20 October 2004, 19:00 CDT

European astronomers said they have discovered many stars in the vicinity of the sun have unusual motions caused by the spiral arms of the Milky Way galaxy.

Astronomers using the European Space Agency's Hipparcos satellite -- which is designed to measure the precise movement of stars -- said the sun's neighborhood appears to be a crossroads for streams of stars coming from several directions.

Some of the stars seem to be coming from more central regions of the Milky Way, moving outward toward the spiral arm containing the sun, then back toward the galactic center, much like asteroids and comets cross Earth's circular orbit.

Although the sun and most stars near it follow an orderly path around the center of the galaxy, Hipparcos observations have revealed groups of so-called rebel stars that move in directions more like the spokes of a wheel.

The rebels, astronomers said, account for about 20 percent of the stars within 1,000 light-years of the sun, which is located about 25,000 light-years from the Milky Way's center.

The satellite's data also show the rebels have little to do with one another, astronomers said. They have different ages, so they cannot have formed at the same time or in the same place. They seem to have been forced together by some as-yet-unknown phenomenon.

Source: United Press International

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