Earth-Sized Exoplanet Is Least Massive Ever Found

April 21, 2009 — Scientists say they’ve discovered a planet outside our solar system that is close to Earth in size — far different from the behemoths they had previously seen so far.

Scientists attending a conference in England said Tuesday that a planet less than twice the size of Earth has been located in a galaxy outside our solar system. The planet, dubbed “e,” was found in the well-known star system Gliese 581. The discovery is the outcome of more than four years of observations using the HARPS spectrograph attached to the 12-foot ESO telescope at La Silla, Chile.

As many as 300 so called exoplanets — or planets outside our solar system — have been discovered, but most are much larger than Earth.

The BBC is quoting scientist Xavier Bonfils of the Grenoble Observatory in France as saying the new planet is the least massive exoplanet ever detected.

Planet Gliese 581 e orbits its host star — located only 20.5 light-years away in the constellation Libra (“the Scales”) — in just 3.15 days. “With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet”, says co-author Xavier Bonfils from Grenoble Observatory.

“The holy grail of current exoplanet research is the detection of a rocky, Earth-like planet in the ‘habitable zone’ — a region around the host star with the right conditions for water to be liquid on a planet’s surface,” researcher Michael Mayor said in a statement released to the press. Because it sits very close to the sun-like star it orbits, the new planet is not within that zone, Mayor said.

Still, the discovery suggests it would not be unlikely to find a habitable Earth-like planet in the Gliese system or elsewhere, Mayor said.

“It is amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995 — Pegasi b,” said Mayor. “The mass of Gliese 581 e is 80 times less than that of 51 Pegasi b. This is tremendous progress in just 14 years.”

Mayor made the announcement at a press conference during the European Week of Astronomy and Space Science.

~ by selahscience on 22 April 2009.