RESEARCH Astronomers report evidence for detecting a rocky planet



The discovery is good news for the idea of life on another planet, expert says.
SAN FRANCISCO CHRONICLE
What might be the first known "Earth-like" planet orbiting a star like our own sun has been reported by European astronomers.
The discovery, if verified by further observations, unveils "a new class of planets" and points to a fresh stage of astronomical research, one that is profoundly relevant to the quest for extraterrestrial life, said Alan Boss of Carnegie Institution in Washington.
That stage is one about which science-fiction buffs have long dreamed: the detection of faraway planets that, like Earth, are relatively small, rocky bodies where plants and creatures might evolve.
"It looks to me like the first discovery of an extrasolar terrestrial-type planet!" said an excited e-mail message to The San Francisco Chronicle from Boss, who was not involved in the discovery but is one of the world's leading authorities on planetary formation. An extrasolar planet orbits a star other than our sun.
Small planet
The planet is too small to be seen directly. The discovery, made by Nuno C. Santos of Portugal and 15 colleagues from France, Switzerland and Chile, was hastened by the development of a sophisticated new telescope that detects slight shifts in the star's motions as it is nudged back and forth by the tiny planet's gravitational pull.
Their find is suspected of being a rocky body that, like Earth, has an iron core. Although perhaps up to 14 times as massive as Earth, it is by far the smallest known planet yet seen that orbits a yellow, "G"-type star similar to our sun.
Another leading expert, Timothy Brown of the National Center for Atmospheric Research in Boulder, Colo., called Wednesday's news "really exciting. The people that do this [research] are among the best anywhere. ... The evidence [for a rocky planet] looks persuasive."
Astronomers have long assumed that life, if it exists elsewhere, almost certainly evolved on a rocky surface like Earth's.
"Previously we had no idea whether rocky planets could be found elsewhere, " Brown said in a phone interview. "This [new discovery] is now evidence that they can be, so it's got to be good [news] for the idea that there's life someplace else."
However, don't place any bets on the likelihood that this particular planet is inhabited: It's so close to its parent star -- much closer than Mercury, the innermost planet of our solar system, is to the sun -- that the surface temperature must exceed 1,000 degrees. The parent star is Mu Arae, which is 50 light years (300 trillion miles) from Earth.
Rather, the discovery underlines the scientific importance of looking for other rocky planets that are placed at more temperate distances from their parent stars. NASA is developing a space-based telescope, Kepler, that will seek such planets; European scientists are developing their own version of such a mission, dubbed Corot.
Solar system
The relatively small mass of the new planet is significant because in our solar system, the smallest planets are rocky bodies -- Earth, where we know life exists, as well as Mars, where scientists speculate conditions once might have supported life -- while the largest worlds, such as Jupiter and Saturn, are giant spheres of gas with small solid cores.
Among scientists who seek extraterrestrial life, G-type stars -- like our sun and Mu Arae -- are presently regarded as the best candidates to illumine inhabited planets. The reason is admittedly simplistic: We live in a G-type system, and at the moment we're the only known life forms in the universe. The designation refers to a class of stars like our sun that are yellowish and have surface temperatures of approximately 10,000 degrees.

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