Kepler-16b
Kepler-16b (formally Kepler-16 (AB)-b) is an exoplanet. 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 Center for Astrophysics | Harvard & Smithsonian, one of the discovery team.
An artist's rendering of the Kepler-16 system, showing the binary star being orbited by Kepler-16b (black body) | |
| Discovery | |
|---|---|
| Discovered by | Laurance Doyle |
| Discovery date | 15 September 2011 |
| Transit (Kepler Mission) | |
| Orbital characteristics | |
| 0.7048 ± 0.0011 AU (105,440,000 ± 160,000 km) | |
| Eccentricity | 0.0069 ± 0.0015 |
| 228.776 ± 0.037 d | |
| Inclination | 90.0322 ± 0.0023 |
| 0.003 ± 0.013 | |
| 106.51 ± 0.32 | |
| 318 ± 22 | |
| Star | Kepler-16 (KOI-1611) |
| Physical characteristics | |
Mean radius | 0.7538 (± 0.0025) RJ |
| Mass | 0.333 (± 0.015) MJ |
Mean density | 0.964 (± 0.047) g cm−3 |
| 14.52 (± 0.7) m/s² | |
| Temperature | 188 K (−85 °C; −121 °F) |
Kepler-16b is also unusual in that it falls inside the radius that was thought to be the inner limit for planet formation in a binary star system. According to Sara Seager, a planetary expert at the Massachusetts Institute of Technology, it was thought that for a planet to have a stable orbit around such a system, it would need to be at least seven times as far from the stars as the stars are from each other. Kepler-16b's orbit is only about half that distance.
Kepler-16b orbits near the outer edge of the habitable zone, but it is a gas giant with surface temperatures around −100 to −70 °C (−150 to −94 °F).