for National Geographic News
The universe beyond our solar system just got wilder.
Astronomers meeting in Colorado this week said they have found a disk of planet-building material around a small, "failed star" called a brown dwarf. The discovery raises the possibility that there may be pint-size solar systems where planets orbit objects far smaller than our sun.
Another team of scientists theorized that some faraway planets could be made mostly out of carbon, and may have a thick layer of diamonds hiding under the surface.
And yet another astronomer announced that he had spotted the smallest planet ever detected outside our solar system.
The results were presented to reporters on Monday in a teleconference from an extra-solar planet meeting held by the American Astronomers Association at the Aspen Center for Physics in Colorado.
Once, scientists believed that planetary systems might be very rare. But since the first planet outside our solar system was found in 1992, more than a hundred planets orbiting stars beyond our system have been discovered.
"This dramatic increase in the number of planets discovered is not by chance," said Michel Mayor, a prominent astronomer at the Geneva Observatory in Switzerland. "It's the improvement of the quality of the spectrometers during these years" that have made the discoveries possible.
Spectrometers separate radiation, including light, into different wavelengths. This allows astronomers to detect bodies that they can't see with telescopes alone.
Up to 20 new planets are being announced this week at the 2005 Winter Conference on Astrophysics, which features more than 200 scientists from around the world.
Alex Wolszczan, the Penn State University astronomer who found the first planets outside our solar system, announced that his team had found the smallest planet yetin the same system as that earlier discovery.
The newly discovered planet, which is about one-fifth the mass of Pluto, is immersed in an extended cloud of gas. It orbits a pulsara former star that exploded and collapsed into a dense object and now spins 160 times per second1,500 light-years away in the constellation Virgo.
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