Geneva (Switzerland) – Scientists at the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) claim to have discovered the smallest exoplanet yet: In the accelerating search for a twin of Earth, Gliese 581 e is only 1.9 times the mass of Earth and may have a similar material structure, but it is too close to its host star to support life as we know it.
The search for exoplanets and the possible discovery of the Earth’s twin is one of the most fascinating research areas for astronomers today. Scientists from the ESO announced earlier today that they have found Gliese 581 e, the fourth planet in the Gliese 581 system which is 20.5 light years away and located in the Libra constellation.
Gliese 581 e is estimated to have 1.9 times the mass of Earth, leading astronomers to believe that the planet has a rocky material structure. However, it orbits its host star in just 3.15 days, which means it is not in the habitable zone. The scientists also adjusted the location of Gliese 581 d, discovered, and now believe that the planet is in the habitable zone: However, Gliese 581 d is estimated to have seven times the mass of Earth that “is probably too massive to be made only of rocky material.” The scientists believe that it may be “an icy planet that has migrated closer to the star.”
In fact, the new observations have revealed that this planet is in a zone where liquid water could exist. “‘d’ could even be covered by a large and deep ocean — it is the first serious 'water world' candidate,” said Stephane Udry, a member of the project group.
The Gliese system has planets with masses of about 1.9 (planet e), 16 (planet b), 5 (planet c), and 7 Earth-masses (planet d).
What makes the discovery so spectacular is the fact that a planet as small as Gliese 581 e was discovered. The first exoplanet (51 Pegasi b) was found in the 51 Pegasi system in 1995. 14 years later, scientists are now able to find planets that are tiny in comparison: The mass of Gliese 581 e is 80 times less than that of 51 Pegasi b.