Scientists say the temperature on the surface of the planet is about a comfy 22C. Its star could almost be a twin of Earth’s Sun, and it probably has water and land.
It was found in the middle of the habitable zone, making it the best potential target for life.
The discovery, announced yesterday, was made via Nasa’s Kepler planet-hunting telescope.
This is the first time researchers using Kepler have confirmed a planet outside Earth’s solar system in the not-too-hot, not-too-cold habitable zone.
Twice before astronomers have announced planets found close to that zone, but neither was as promising.
One was disputed; the other is on the hot edge of the zone.
Meanwhile, the Planetary Habitability Laboratory (PHL) at the University of Puerto Rico in Arecibo, home of the world’s largest single-dish radio telescope, is compiling a catalogue of habitable worlds.
So far only two marginally Earth-like planets have been confirmed as fully matching the criteria for habitability.
But the Habitable Exoplanets Catalog (HEC) identifies more than 15 planets and 30 “exo-moons” as potentially habitable.
Future studies with powerful new telescopes will be needed to confirm whether any of these candidates really could harbour life.
Astronomers have already established the existence of more than 700 exo-planets and thousands more are awaiting confirmation.
Most are hot gas giants, such as Jupiter and Neptune, orbiting close to their stars.