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# Posted: 7 Feb 2006 16:07
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Astronomers find smallest extrasolar planet yet
This artist's illustration shows an icy/rocky planet orbiting a dim star. Astronomers detected an extrasolar planet five times as massive as Earth circling a red dwarf, a relatively cool star. The distance between the planet, designated OGLE-2005-BLG-390Lb, and its host is about three times greater than that between the Earth and the Sun. The planet's large orbit and its dim parent star make its likely surface temperature a frigid minus 364 degrees Fahrenheit (minus 220 degrees Celsius).
Using a relatively new planet-hunting technique that can spot worlds one-tenth the mass of our own, researchers have discovered a potentially rocky, icy body that may be the smallest planet yet found orbiting a star outside our solar system.
The discovery suggests the technique, gravitational microlensing, may be an exceptional technology for finding distant planets with traits that could support life.
"This is an important breakthrough in the quest to answer the question 'Are we alone?'" said Michael Turner, assistant director for the National Science Foundation (NSF) mathematical and physical sciences directorate. "The team has discovered the most Earth-like planet yet, and more importantly, has demonstrated the power of a new technique that is sensitive to detecting habitable planets. It can probe a much greater portion of our galaxy and is complementary to other techniques."
Located more than 20,000 light years away in the constellation Sagittarius, close to the center of our Milky Way galaxy, planet OGLE-2005-BLG-390Lb is approximately five-and-a-half times the mass of Earth.
Orbiting a star one-fifth the mass of the sun at a distance almost three times that of Earth's orbit, the newly discovered planet is frigid: the estimated surface temperature is -364 degrees Fahrenheit (-220 degrees Celsius).
Although astronomers doubt this cold body could sustain organisms, researchers believe gravitational microlensing will bring opportunities for observing other rocky planets in the "habitable zones" of stars - regions where temperatures are perfect for maintaining liquid water and spawning life.
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