Astronomers snap extrasolar image: shot may be the first of an exoplanet orbiting a sunlike star.

After years of false alarms, astronomers may finally have recorded the first image of a planet orbiting a sunlike star beyond the solar system.

The body, about eight times Jupiter's mass, lies exceptionally far from its presumed parent star--roughly 11 times Neptune's average distance from the sun.

"If this object is a planet at such a wide separation, it would challenge our conceptions of planet and companion formation," says Adam Burrows of Princeton University.

In an article posted online September 10 at arxiv.org/abs/0809.1424, codiscoverers David Lafreniere, Ray Jayawardhana and Marten H. van Kerkwijk of the University of Toronto caution that there's a chance that the object merely resides in the same part of the sky as the star but is not gravitationally bound to it.

But if the body does orbit the young sunlike star, which has the unwieldy name 1RXS J160929.1-210524, it could pose a problem for planet formation theories. A widely accepted model suggests that the planet-forming disks of gas, dust and ice surrounding newborn stars concentrate material close to their stars.

"The bulk of the material from which planets might form is significantly closer to the parent star," Burrows says.

The outermost parts of such disks wouldn't contain enough material to assemble a Jupiter-mass planet at the distance from the star--330 astronomical units, or 330 times the separation between Earth and the sun--at which the team found the faint object.

"At hundreds of astronomical units from the star, the density of material in the disk is so low that any small seed of planet would not be able to grow [large] enough before the disk vanishes in a few million years," Lafreniere says.

He and his colleagues found the object by using a special optics system on the Gemini North telescope atop Hawaii's Mauna Kea. They scoured the vicinity of some 85 stars belonging to the Upper Scorpius association. Stars in this group lie 500 light-years from Earth and are only about 5 million years old. The sun is 4.55 billion years old.

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Most of the more than 300 extrasolar planets astronomers have discovered since 1995 have been detected indirectly. Though researchers imaged an exoplanet around a brown dwarf in 2004, no one has recorded an image of a planet orbiting a sunlike star.

Astronomers will need to track the motion of the newly discovered body across the sky for one to two years to determine whether it moves in sync with the star, Jayawardhana says.