Dusting for New Planets

By Maia Weinstock|Saturday, March 01, 2003
RELATED TAGS: NEW PLANETS
The hunt for planets around other stars just got easier. Alice Quillen of the University of Rochester and undergraduate Stephen Thorndike of Alfred University, also in New York, have found a way to detect worlds too small or slow-orbiting to show up in current surveys. This method has revealed what may be a Neptune-size body circling Epsilon Eridani, one of the closest sunlike stars.

Astronomers have identified more than 100 planets orbiting stars outside our solar system, primarily by monitoring the way a planet's gravity tugs its star back and forth. That technique most readily picks up Jupiter-size planets in fast, Mercury-like orbits, objects unlike anything in our solar system. A newer approach, looking for the shadow of a planet passing in front of its star, has similar limitations. Quillen and Thorndike instead study subtle gravitational disturbances in the dust rings that surround many stars less than a billion years old. As a test, the researchers observed infrared emissions from the faint dust around Epsilon Eridani and compared them with computer simulations of clumping patterns. Their results indicate a possible planet approximately the mass of Neptune—the smallest yet seen around a sunlike star—orbiting every 280 years. That period is similar to the 164-year orbit of the real Neptune. "We were totally surprised," Quillen says.

Previous studies have revealed a Jupiter-mass planet in a roughly Jupiter-like orbit around Epsilon Eridani. If the new planet checks out, Epsilon Eridani starts to look a lot like our solar system. Quillen wants to use NASA's new Space Infrared Telescope Facility to get a clearer view of the dust ring. Earth-like planets, however, remain beyond the limits of today's searches.





 
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