Discovery date 12/22/2011 (announced) Discovery site Kepler telescope | Discoverer(s) Charpinet et al. Discovery status Published | |
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Kepler-70b (formerly known as its Kepler Object of Interest designation KOI-55.01; sometimes listed as KOI-55 b) is an exoplanet discovered orbiting the subdwarf B star (sdB) Kepler-70. It orbits its host along with another planet, Kepler-70c, both of which orbit very close to their host star. Kepler-70b completes one orbit around its star in just 5.76 hours, one of the shortest orbital periods of any exoplanetary system yet discovered, only second to the exoplanet PSR 1719-14 b with a period of 2.2 hours. It is also the hottest exoplanet as of mid-2013, with a surface temperature of 7,143 K (6,870 °C; 12,398 °F). Its density is 5500 kg/m3 which is not much different from Earth.
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Mass, radius and temperature
Kepler-70b is likely a rocky exoplanet with a mass of 0.44 M⊕ and a radius of 0.76 R⊕. It has a surface temperature of 7,143 K (6,870 °C; 12,398 °F), one of the hottest known surface temperatures on any exoplanet. It is even hotter then the surface of the Sun, by about ~1500 K.
Composition
Kepler-70b is currently made of iron which means it's probably just a core orbiting its star Kepler-70,but a long time ago,it could've been made of other stuff such as rock or hydrogen,but got too close to It's parent star and then it was vaporized and only the core survived the heat so now it is probably just a core orbiting the star.
Orbit
The exoplanet has an orbit period shorter than any exoplanet known to date, with an orbital period of 5.76 hours (345 minutes). This comes in second to the exoplanet PSR 1719-14 b, which, coincidentally, orbits a stellar remnant, much like the planets of Kepler-70.
Host star
The host star, Kepler-70 (also formally known as KOI-55, 2MASS J19452546+4105339 or KIC 5807616), is a subdwarf B-type star that has left its red giant stage of its lifetime – according to the Extrasolar Planets Encyclopedia – about 18.4 million years ago. It has a surface temperature of 27730 ± 270 K, nearly 6 times as hot as the surface temperature of the Sun, which has a surface temperature of 5778 K. The star has a mass of 0.496 M☉ and a radius of 0.203 R☉ It is expected to become a white dwarf in the future, after fusing the remaining helium in its core, and shrink in size to around the size of the Earth.
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 14.87. Therefore, Kepler-70 is too dim to be seen with the naked eye.
Encounters
Kepler-70c passes 240,000 kilometres (150,000 mi) away from Kepler-70b during their closest approach, possibly causing tidal forces against each other. This is currently the closest recorded approach between planets.
Cultural impact
According to the main author of the paper in Nature which announced the discovery of the two planets, Stephane Charpinet, the two planets "probably plunged deep into the star’s envelope during the red giant phase, but survived.” However, this is not the first sighting of planets orbiting a post-red giant star - numerous pulsar planets have been observed, but no planet has been found with such a short period around any star, whether or not on the main sequence.
Origins
The two planets were most likely gas giants which spiraled inward toward their host star, which subsequently became a red giant, vaporizing much of the planets except for parts of their solid cores, which are now orbiting the sdB star.