Scientists are claiming to have discovered six new planets around stars outside the solar system, almost doubling the number known. The putative planets, each having roughly the mass of Jupiter, all seem to move in rather elliptical orbits--an observation that has theorists scratching their heads.
Details of the sightings became widely available on 23 June, when Jean Schneider of the Observatoire de Paris in France posted them on his Web site, the Extrasolar Planets Encyclopedia (wwwusr.obspm.fr/planets/). Many of the results are expected to be announced at a meeting on Protostars and Planets, to be held in Santa Barbara, California, from 5 to 12 July.
The findings appear to challenge theories about how planets form. "We had thought that objects of this mass would form on circular orbits,'' says Alan Boss of the Carnegie Institution of Washington, developing as the agglomeration of many small objects whose orbits would average out into a circle.
The detections of the new planet candidates were all made with the "Doppler" technique, in which the wobble of the parent star toward and away from an observer is recorded. According to Schneider, three possible planets were spotted by a team led by Martin Kurster, using the European Southern Observatory in La Silla, Chile. Michel Mayor of the Geneva Observatory, Didier Queloz of the Jet Propulsion Laboratory, and colleagues spotted three others, one of which was also seen by Geoff Marcy of San Francisco State University, Paul Butler of Anglo Australian Observatory, and Steven Vogt at University of California, Santa Cruz, using the 10-meter Keck Telescope in Hawaii.