Kepler-11 d

Kepler-11d is an exoplanet discovered in the orbit of the sun-like star Kepler-11. It is named for the telescope that discovered it, a NASA spacecraft named Kepler that is designed to detect Earth-like planets by measuring small dips in the brightness of their host stars as the planets cross in front. This process, known as the transit method, was used to note the presence of six planets in orbit around Kepler-11, of which Kepler-11d is the third from its star. Kepler-11d orbits Kepler-11 well within the orbit of Mercury approximately every 23 days. The planet is approximately six times more massive than the Earth, and has a radius that is three and a half times larger than that of Earth's. It is, however, far hotter than Earth is. Its low density, comparable to that of Saturn, suggests that Kepler-11d has a large hydrogen–helium atmosphere. Kepler-11d was announced with its five sister planets on February 2, 2011 after extensive follow-up studies.

==Name and discovery== As with all exoplanets, Kepler-11d is named first for its host star, Kepler-11. Because Kepler-11d was announced at the same time as the five other planets in the system, their names are sorted by their distances from the host star; thus, because Kepler-11d is the third planet from Kepler-11, it was given the designation d. Kepler-11 was named for the Kepler space telescope, a NASA Earth-trailing satellite purposed with discovering Earth-like planets in a small area of the sky between the constellations Cygnus and Lyra by observing planets that transit, or cross in front of, their host stars with respect to Earth. The transit causes the star's brightness to dim slightly and at a regular rate, a phenomenon that the Kepler satellite notes till future study can prove or disprove the existence of a planetary body. Kepler-11d was flagged by Kepler-11, given the designation KOI-157.