Washington, July 10 : Radio observations of Orion Nebula have indicated that small fraction of sun-like stars have enough surrounding dust to make Jupiter-sized planets, according to a report by astronomers.
The report was prepared by astronomers at the University of California, Berkeley, the California Institute of Technology (Caltech) and the Harvard-Smithsonian Center for Astrophysics.
"We think that most stars in the galaxy are formed in dense, Orion-like regions, so this implies that systems like ours may be the exception rather than the rule," said lead author Joshua Eisner, a Miller postdoctoral fellow at UC Berkeley.
This is consistent with the results of current planet searches, which are finding that only about 6 percent of stars surveyed have planets the size of Jupiter or larger.
The Orion Nebula is a brilliant cluster only a million years old and glowing with the light of newly formed stars like a jewel in the sword of the hunter Orion.
"The cluster is also very dense, with 1,000 stars packed into a region several light years on a side. For comparison, in the neighborhood of the sun, there's only one star within that volume of space," said Eisner.
Four billion years ago, however, the sun may have been in a dense, open cluster like Orion.
Because open clusters like Orion eventually become gravitationally unbound, they disperse over the course of billions of years, and as a result, the sun's birth neighbors are long gone.
"Studying star clusters like the Orion Nebula Cluster helps our understanding of the typical mode of star and planet formation," said Eisner.
The astronomers' observations of Orion's central region of more than 250 known stars showed that only about 10 percent emit 1.3-millimeter wavelength radiation typically emitted by a warm disk of dust.
Even fewer - less than 8 percent of stars surveyed - were judged to have dust disks with masses greater than one-hundredth the mass of the sun, a mass thought to be the lower limit for formation of Jupiter-sized planets.
The average mass of a protoplanetary disk in the region was only one-thousandth of a solar mass, the researchers calculated.
Eisner noted that previous surveys he and Carpenter have conducted of other young, open clusters that are older or younger than Orion show an evolutionary trend in the average masses of disks in the different regions.
Older clusters tend to show less dust, perhaps because much of it has already gathered into planets.
Previous surveys of another lower-density, star-forming region - the Taurus cluster - showed that more than 20 percent of its stars have enough mass to form planets.