Munich, April 22 (ANI): Scientists have announced the discovery of the lightest exoplanet found so far, which is only about twice the mass of our Earth.
The planet, "e", lies in the famous star system Gliese 581.
The finding is the outcome of more than four years of observations using the most successful low-mass-exoplanet hunter in the world, the HARPS spectrograph attached to the 3.6-metre ESO telescope at La Silla, Chile.
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," said co-author Xavier Bonfils from Grenoble Observatory.
Being so close to its host star, the planet is not in the habitable zone.
From previous observations, also obtained with the HARPS spectrograph at ESO's La Silla Observatory and announced two years ago, this star was known to harbour a system with a Neptune-sized planet (ESO 30/05) and two super-Earths (ESO 22/07).
With the discovery of Gliese 581 e, the planetary system now has four known planets, with masses of about 1.9 (planet e), 16 (planet b), 5 (planet c), and 7 Earth-masses (planet d).
"It is amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995 - the one around 51 Pegasi," 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," he added. (ANI)