Astronomers craving their first image of a planet beyond our solar system now have fresh targets to explore: newly identified siblings of Beta Pictoris, the most famous dust-shrouded star in the sky. An extensive survey suggests that more than two dozen stars were conceived about 12 million years ago in the same womb as Beta Pic, thus exposing the closest and youngest stellar group yet known. Astronomers hope that gas-giant planets, still warm from their birth, will be visible around some of the stars.
Beta Pic's fame dates to 1983, when a satellite photographed its vast cocoon of dust--the first glimpse of a suspected planetary system in the making. Theories predict that most stars arise in groups, so astronomers expected the apparently juvenile Beta Pic to have nearby companions hatched from the same gaseous nursery. However, the first confirmed nest mates didn't turn up until 1999, when a team analyzed two youthful dwarf stars with trajectories that mimicked Beta Pic's path in space. The dwarfs raised hopes that more siblings were out there.
The family has indeed grown, according to a report in the 20 November issue of Astrophysical Journal Letters. Astronomers Ben Zuckerman and Inseok Song of the University of California (UC), Los Angeles, and their colleagues describe 17 single and multiple star systems moving through space with Beta Pic, at an average distance of just 100 light-years from Earth. Each star also exhibits at least one hallmark of adolescence, such as copious x-rays, rapid spin, or a dusty disk of its own. "The chance that we have misidentified random stars as members of the Beta Pic group is extremely small," Song says.
The group's youth and proximity make the stars "fantastically suitable for direct searches for warm newborn planets," says astronomer Ray Jayawardhana of UC Berkeley, because such planets would shine brightly in infrared light. Still, Jayawardhana and astronomer Thomas Greene of NASA's Ames Research Center in Mountain View, California, believe it's not yet settled whether the stars shared a birthplace, all arising at roughly the same time in the same cluster. "If the original cloud was big enough, it could have formed several small clusters with age differences of 5 or 10 million years," Greene notes.