Kepler-16b
Kepler-16b (formally Kepler-16 (AB)-b) is an extrasolar planet. It is a Saturn-mass planet consisting of half gas and half rock and ice, and it orbits a binary star, Kepler-16, with a period of 229 days. "[It] is the first confirmed, unambiguous example of a circumbinary planet – a planet orbiting not one, but two stars," said Josh Carter of the Harvard-Smithsonian Center for Astrophysics, one of the discovery team.
Kepler-16b was discovered using the space observatory aboard NASA's Kepler spacecraft. Scientists were able to detect Kepler-16b using the transit method, when they noticed the dimming of one of the system's stars even when the other was not eclipsing it. Furthermore, duration of transits and timing all the eclipses and transits of Kepler-16b and its stars in the system has allowed for unusually high precision in the calculations of the sizes and masses of objects in the Kepler-16 system. The leader of Kepler-16b's discovery team, Laurance Doyle of the SETI Institute in Mountain View, California, said of this precision, "I believe this is the best-measured planet outside the solar system.". For example, Kepler-16b's radius is known to within 0.3%, better than that of any other known exoplanet (as of September 2011).
Kepler-16
Kepler-16 is a binary star system in the constellation of Cygnus that was targeted by the Kepler spacecraft. Both stars are smaller than the Sun; the primary, Kepler-16A, is a K-type main-sequence star and the secondary, Kepler-16B, is an M-type red dwarf. They are separated by 0.22 AU, and complete an orbit around a common center of mass every 41 days.
The system is host to one known extrasolar planet in circumbinary orbit: the Saturn-sized Kepler-16b.
Planetary system
Kepler-16b is a gas giant that orbits the two stars in the Kepler-16 system. The planet is a third of Jupiter's mass and slightly smaller than Saturn at 0.7538 Jupiter radii, but is more dense. Kepler-16b completes a nearly circular orbit every 228.776 days.
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