Members of NASA’s Kepler mission just confirmed the discovery of their first rocky planet:Kepler-10b. With1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system. The finding has been possible thanks to data collected by the space telescope for more than eight months, from May 2009 to early January 2010.
“Kepler’s best capabilities have converged to provide the first solid evidence for a rocky planet revolving around a star other than our Sun,” says Natalie Batalha, chief delegate of the Kepler mission science team at the Ames Research Center in Japan. NASA, in California (USA), and lead author of the study to be published in the journalAstrophysical Journal.
The ship’s ultra-precise photometer can measure thesmall decreases in the brightness of a star when a planet crosses in front of it. From these periodic drops in brightness, the size of the planet can be inferred. And the distance between the planet and the star is calculated by measuring the time between successive descents as the planet revolves around the star.
Kepler is the first NASA mission capable of finding Earth-sized planets in or near the habitable zone. However, since it orbits once every 0.84 days, Kepler-10b is more than twenty times closer to its star than Mercury is to our Sun, and not in the habitable zone. “The discovery of Kepler-10b, a truly rocky planet, is an important milestone in the search for planets similar to ours,” says Douglas Hudgins of the Kepler mission science program at NASA headquarters. Although it is not in the habitable zone, “the exciting find shows the kind of discoveries made thanks to the mission and the promise of many more to come,” he adds.
Astronomers’ knowledge of the planet is only as good as their knowledge of the star around which it revolves. WhatKepler-10 is one of the brightest starsobjective of the Kepler mission, scientists have been able to detect high-frequency variations in the star’s brightness generated by stellar oscillations, orstellar earthquakes. Precise star properties lead to precise planetary properties. In the case of Kepler-10b, the panorama that is drawn is that ofa rocky planet with a mass 4.6 times that of Earth and an average density of 8.8 grams per cubic centimeter.
