A new 'Earth'

The announcement was greeted with enthusiasm by many U.S. astronomers.

"This appears to be the very first detection of a whole new habitable world, with liquid water and the possibility of life. It's a huge milestone in astronomy," Alan P. Boss, an astronomer withthe Carnegie Institution in Washington, said in a phone call to The Chronicle from Sweden, where he is attending a meeting. The lead author of the discovery report, Stephane Udry of the Geneva Observatory in Switzerland, said the planet's sun is named Gliese 581, one of the galaxy's extremely common "red dwarfs." It lies in the constellation Libra, the Scales, about 20.5 light-years away from Earth -- a relatively close neighbor compared with other exoplanets that have been detected thousands of light-years away.