More Trouble for First Extrasolar Planet

A team of California astronomers has come up with new evidence disputing the existence of the first planetlike object found around a star like our sun. The putative planet, detected some 18 months ago at the star 51 Pegasi, has already faced more than its share of scrutiny. No more than a slight wobble of 51 Peg had suggested the presence of the companion. It's the same kind of clue that has led observers to what they think are eight more planets outside our solar system, but it leaves plenty of room for doubt. Just 3 months ago, for example, one astronomer claimed in Nature that the planet searchers might have been fooled by a large-scale sloshing on the star's surface--an issue that is still unresolved (see ScienceNOW, 26 February). Now, according to a News story in tomorrow's issue of Science,* astronomers at the California Institute of Technology (Caltech) and NASA's Jet Propulsion Laboratory, both in Pasadena, believe the wobble may be the signature of a dual-star system called a binary. Using a powerful telescopic array called an infrared interferometer, Caltech's Xiaopei Pan and co-workers may have "resolved" the 51 Peg system: observed a spatial structure inconsistent with a simple point of light. The star itself is almost certainly too small to appear as anything other than a point, and a planet should not be visible. So the preliminary results--which have been described only at conferences and on the World Wide Web--could suggest that the object orbiting 51 Peg is a dim companion star, not a planet.

Still, 51 Peg does not show other hallmarks of a close binary, so astronomers are reacting cautiously. "It would be such a blockbuster result," says David Latham of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "It's not impossible, but it's not what I expected." For that reason, planet hunters haven't given up on their oldest find yet.

* For more details, Science Online subscribers can link to the full text of the Research News story.