Tuesday, April 21, 2009

Smallest Exoplanet Yet is Found

A new exoplanet discovery was announced today at the European Joint National Astronomy Meeting in England. The planet is called Gliese 581 e, the smallest extra solar planet yet found with a lower limit of mass of about 1.9 times the size of Earth. The star, Gliese 581, around which the planet orbits is 20.5 light years away in the constellation Libra. Gliese 581 is a low-mass, red dwarf star, the kind most likely to have Earthlike planets.

So far, there have been more than 340 exoplanets discovered, but most have been large "Hot Jupiters" that cannot harbor life. Veteran planet hunter Michel Mayor of the Geneva Observatory described his team's findings at the conference. Mayor and his colleagues, detected the tiny planet indirectly by the wobble method, the pull the planet exerts on its parent star.

"Gliese 581 is a truly fascinating exoplanet system," said planetary scientist Sara Seager of MIT. "It is like a gift that keeps on giving."

The holy grail of exoplanet research is to find a planet that combines both, the approximate mass of Earth and conditions favorable for water. Planets circling around their host star at a distance where liquid water can exist are in the so-called "habitable zone."

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