Possible New Planets Discovered

Two teams of astronomers searching for signs of other solar systems have independently discovered a disk around a star that may be forming -- or already may have formed -- planets.

The disk of dust and gas, billions of miles across, surrounds a star trillions of miles from Earth, and is thought to be the right age for forming planets. A dozen other planets and possible planets have been found beyond the solar system recently, hinting that planets may be common in the universe. If so, that means life may also be common.

The joint discovery was made by one team from the

Harvard-Smithsonian Center for Astrophysics in Cambridge,

Mass., and the University of Florida in Gainesville. They used the 4-meter (13-foot diameter) Blanco Telescope in La Serena, Chile. A second team, from the National Aeronautics and Space Administration's (NASA) Jet Propulsion Laboratory in California, and Franklin & Marshall College in Lancaster, Pa., used the 10-meter (33-foot diameter) Keck II Telescope on Mauna Kea, Hawaii.

The newly discovered disk surrounds a star known as

HR 4796A in the southern constellation Centaurus. HR 4796A is roughly 20 times brighter than the Sun and two or three times more massive. The disk itself appears to be roughly 23 billion miles

across, or 250 times the distance from Earth to the Sun.

Harvard astronomers also were part of a team that discovered a planet around a sunlike star in the Northern Cross constellation last May.

"What's exciting is that we are looking at a disk just at the time it is forming planets or has recently done so," says Ray Jayawardhana of the Harvard-Smithsonian Center for Astrophysics. The Sun formed its planets between 4 and 5 billion years ago, so the new discovery is like looking back to that time. Jayawardhana found the disk while making observations for his PH.D. thesis.

Hugh Van Horn, of the National Science Foundation,

comments that, "Numerous discoveries of planetary systems [beyond our own] have shown that we have much to learn about the process of planet formation. The exciting new observations will certainly help to advance our understanding of the planet-forming process."