Extrasolar planet with an Earthlike orbit.

Tracking the wobbling motion of several hundred nearby stars, astronomers over the past 4 years have found evidence of some 20 planets outside the solar system. The latest find, announced July 29, stands out from the crowd. Its orbit more closely resembles that of Earth than any extrasolar planet previously found.

The planet lies an average of 137 million kilometers from its parent, the sunlike star iota Horologii. That's 92 percent of the distance between Earth and the sun. The planet's mass, however, is at least 2.26 times that of Jupiter, or 718 times that of Earth, report Martin Kurster of the European Southern Observatory in Santiago, Chile, William D. Cochran of the University of Texas at Austin, and an international team of colleagues.

Rather than having a solid surface, the planet is most likely a giant blob of noxious gases like Jupiter and is unlikely to support life, Cochran says. However, "if such a planet has a system of satellites around it, they would be an excellent place for life to develop," he adds.

Geoffrey W. Marcy of San Francisco State University and the University of California, Berkeley says there's another reason he finds the new object intriguing. Like the other 11 extrasolar planets that reside farther than 29 million km (20 percent of the Earth-sun distance) from their parent star, this one has an elliptical orbit. "This new planet adds to the suspicion that our solar system with its neat, circular, coplanar orbits, may be the exception rather than the rule."