The planet Gliese 581g has just been placed as number one on the list of the five planets outside our Solar System that could support life. The star was discovered two years ago by researchers at the University of Santa Cruz, California, butits existence was questionedby the scientific community. Now, new analyzes published in the magazineAstronomical Notesconfirm their presence.
It is a rocky planet, with a radius no more than 1.5 times that of the Earth, and receives from its star, the so-called Gliese 581, the same amount of light that our planet receives from the Sun. In addition, it occupies the narrow orbital strip in which theadequate temperature to allow the existence of liquid water, an essential element so that life, as we know it, is possible. That is why Gliese 581g is the most Earth-like exoplanet known to date. This claim is based on the Earth Similarity Index, a measure that is based on various parameters and ranges between 0 and 1. The index for Gliese 581g is 0.92, which puts it ahead of Gliese 667c, discovered last year.
The reason why other scientists could not confirm the existence of the new star is, according to the team from the University of Santa Cruz, that the exoplanets that revolve around Gliese 581follow a circular orbitand not elliptical. Assuming the circular orbit, scientists have managed to measure with the HARPS instrument (High Precision Radial Velocity Planet Finder) a strong signal that confirms the existence of Gliese 581g.
It is also the first evidence of two potentially habitable exoplanets orbiting the same star. The Planetary Habitability Laboratory (PHL), of the University of Puerto Rico, has decided to include Gliese 581g in the Catalog of Habitable Exoplanets. “The controversy around Gliese 581g will continue, but based on the new evidence, we have decided to include it in the catalog until more is known about the architecture of this interesting star system,” explained Abel Méndez, PHL director. The list consists of Gliese 581g, Gliese 667Cc, Kepler-22b, HD85512 and Gliese 581d.
