Astronomers deem to have found the first Earth-sized planet outside our solar system that is likely to support liquid water and therefore life. Gliese 581g was discovered orbiting a nearby star at a distance that places it squarely in the "habitable zone" where liquid could exist on its surface.
According to Prof Steven Vogt, who led the team that discovered it, the planet is a similar size to Earth and its mass indicates that it is probably rocky with a definite surface and has enough gravity to hold an atmosphere.
It is as still unknown whether water does exist on the planet or what kind of atmosphere it has. But because conditions are perfect for liquid, which is always a precursor for life on Earth, Prof Vogt believes "that chances for life on this planet are 100 percent".
It is believed that Gliese 581g, has a mass three to four times that of Earth and an orbital period of just under 37 days and is located 20 light years away from Earth in the constellation Libra. The planet is tidally locked to the star, which means that one side is always facing the star and basking in perpetual daylight, while the side facing away from the star is in perpetual darkness.
The researchers estimate that the average surface temperature of the planet is between -24 and 10 degrees Fahrenheit (-31 to -12 degrees Celsius). The surface gravity would be about the same or slightly higher than Earth's, so that a person could easily walk upright on the planet, Prof Vogt said.