August 26, 2010 Telescope Detects Possible Earth-Size Planet By KENNETH CHANG Astronomers are quickly closing in on Earth-size planets elsewhere in the galaxy as they find planetary systems that look more and more like our solar system. Scientists working with NASA’s Kepler satellite reported Thursday that they might have spotted a planet just 1.5 times the diameter of Earth around a Sun-like star 2,000 light-years away. If that planet is made of similar stuff as Earth, its mass would be three to four times as much. “We’re still in the process of confirming this candidate is a planet,” said Matthew Holman, of the Harvard-Smithsonian Center for Astrophysics, during a NASA-sponsored news conference on Thursday. Dr. Holman is the lead author of an article describing the discoveries that the journal Science published on its Web site. This is the first announcement of a candidate Earth-size planet by the Kepler mission, which launched a one-ton orbiter in March 2009 to search for planets like ours. The planet was among more than 700 candidate planets that the team announced spotting in June. The Kepler team also observed, more definitively, two Saturn-size planets around the same star, known as Kepler-9. On Tuesday, a European team reported what may be an even smaller planet, with mass as little as 1.4 times that of Earth, around a star 127 light-years away. In the past 15 years, astronomers have discovered close to 500 such extrasolar planets. At first, they uncovered huge gas giant planets that orbited extremely close to the stars. But as detection methods improved, astronomers began to find planets closer in size to Earth and planetary systems that contain nearly as many planets as our solar system. The Earth-size planet seen by the European astronomers appears to be one of seven circling the star, HD 10180, located in the constellation Hydrus. Christophe Lovis of the University of Geneva, who led the observations, said the group was certain about the existence of five of the planets, all about the size of Neptune, but squeezed into orbits closer to the star than Mars is to the Sun. Dr. Lovis said they were slightly less certain about the smallest planet. “For this one, we have about 1 percent false alarm possibility,” Dr. Lovis said. “For us, 99 percent is just not enough to be completely sure.” The team also tentatively detected a larger, Saturn-size planet farther from the star. Neither of the slightly-bigger-than-Earth planets is Earth-like. Both have orbits very close to their stars that would sear the surfaces. “If one particular word can describe planetary systems today, it’s ‘diverse,’ “ said Douglas N. C. Lin, a professor of astronomy and astrophysics at the University of California, Santa Cruz, who not involved with either team. “Planets are common, and their properties are diverse.” Photo Caption: An artist’s rendering shows the two Saturn-sized planets discovered by NASA’s Kepler mission, which also found a planet sized similarly to Earth. added by: EthicalVegan
