The first "rocky" planet to be discovered by NASA's Kepler Mission, Kepler-10b is an exoplanet 1.4 times the size of our Earth. An exoplanet is any identified planet outside of our own Solar System. As of June 2013, there have been 866 exoplanets identified, located around 671 stars, nearly all within the Milky Way Galaxy. Kepler-10b has a density 4.6 times that of Earth, or similar to an iron dumbbell. This planet orbits its star, Kepler-10, once every 0.84 days (20 hours) and is 20 times closer to its star than Mercury is to our Sun. At such close range, Kepler-10b does not lie in the habitable zone, the region in which liquid water could exist on a planet's surface. Therefore, it is unlikely any life exists on its surface. The planet is also tidally locked to its parent star, meaning only one side ever faces the star.
Kepler-10 was the first star discovered by the Kepler Mission that could potentially have a small planet transiting across it. This was later confirmed by observational data from the Keck Observatory in Hawaii. This artist's visualization suggests the rocky composition of Kepler-10b with no bands of gas present. Being tidally locked, the surface on the star-facing side is thought to be molten and glowing, while the surface on the side facing away from the star is be solid and rocky.
Launched in 2009, the Kepler spacecraft measures the light output of 150,000 stars simultaneously. The data from each star are then analyzed in order to look for periodic drops in the light curve. These drops in brightness could indicate the presence of an orbiting planet passing in front of its host star, blocking some of its light. This is called a transit. Three or more transits of equal periods are needed to catalog an object as a planet candidate.