Astronomers have discovered what they claim is the smallest-ever rocky planet outside our solar system, named Kepler-10b.
A team at NASA says that its Kepler mission has confirmed the discovery of the exoplanet, measuring 1.4 times the size of Earth -- its discovery is based on eight months of data collected by the spacecraft from May 2009 to Jan 2010.
According to the astronomers, the rocky planet has a mass 4.6 times that of Earth and with an average density of 8.8 grams per cubic centimetre, it's similar to that of an iron dumbbell, the Astrophysical Journal reported.
"All of Kepler's best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun," Natalie Batalha, Kepler's deputy science team leader at NASA's Ames Research Center in Moffett Field, California, said.
She added: "The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it's beginning to pay off."
Since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer to its star than Mercury is to our sun and not in the habitable zone, say the NASA astronomers.
"The discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own. Though 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 Douglas Hudgins, Kepler programme scientist at NASA in Washington.
Because Kepler-10 is one of the brighter stars being targeted by Kepler, the NASA team was able to detect high-frequency variations in the star's brightness generated by stellar oscillations. This analysis allowed scientists to pin down Kepler-10b's properties.
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet's surface.