NASA’s orbital telescope Kepler has found the smallest-ever planet outside of the Solar System.

­The new planet, called Kepler 10-b, was first spotted in July 2009 as it was transiting the face of its star about 560 light years from the sun. Since then the observatory team has gathered conclusive evidence before reporting their find.

Most exoplanets found so far are large gaseous giants like Jupiter. However, smaller rocky worlds are of more interest to scientists, as they may have an environment with liquid water, which would make Earth-like life possible on them.

Judging from its gravitational pull measured by astronomers, the new planet is about 4.6 times heavier than Earth. With diameter of 1.4 that of Earth, it suggests a rocky composition, the Kepler team reported.

However the Kepler 10-b is unlikely to have any life on it since it orbits its star 23 times closer than Mercury’s orbit of the sun. At this close range, the planet always faces the star with one side, similar to how the moon always faces Earth, and the temperature during its daytime is hot enough to melt iron.

"Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come," said Kepler program scientist Douglas Hudgins.