Kepler-70c (formerly called KOI-55.02; sometimes listed as KOI-55 c) is one of two postulated

exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

orbiting the sdB star

Kepler-70 Kepler-70, also known as KIC 5807616 and formerly as KOI-55, is a star in the constellation Cygnus with an apparent visual magnitude of 14.87, and is 4200 light-years away. This is too faint to be seen with the naked eye; viewing it requ ...

. Their discovery was announced in 2011. However, later research suggests that the two exoplanets probably do not exist, and that "pulsation modes visible beyond the cut-off frequency of the star" were a more likely explanation for the signals believed to indicate exoplanets. This is not proven with certainty one way or the other. If it exists, Kepler-70c orbits its host along with another planet,

Kepler-70b Kepler-70b (formerly known as its Kepler Object of Interest designation ''KOI-55.01''; sometimes listed as KOI-55 b) is one of two postulated exoplanets orbiting the subdwarf B star (sdB) Kepler-70. The other planet is Kepler-70c, and both planet ...

. Both of these planets orbit very close to their host star. Kepler-70c completes one orbit around its star in just 8.232 hours. It is also one of the hottest

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s as of mid-2013. It has a high density, suggesting that it is largely composed of metals.

passes 240,000 km away from Kepler-70c during their closest approach. This is currently the closest recorded approach between planets. Such orbital configuration is relatively stable due to orbital resonance between planets and small

Hill sphere The Hill sphere of an astronomical body is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sp ...

s of planets due to proximity of the star. According to the main author of the paper in ''

Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

'' 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 Pulsar planets are planets that are found orbiting pulsars, or rapidly rotating neutron stars. The first such planets to be discovered were around a millisecond pulsar and were the first extrasolar planets to be confirmed as discovered. History ...

have been observed, including

one 1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of ''unit length'' is a line segment of length 1. I ...

that orbits closer to its host star, and consequently in a shorter time than, any other planet.

Origins

The two planets may have started out as a pair of

gas giants A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant ...

which spiraled inward toward their host star, which subsequently became a red giant. This engulfed the planets, evaporating all but their solid cores, which now orbit the sdB star. Alternatively, there may only have been one gas giant engulfed in this way, with the rocky/metallic core having survived evaporation but fragmented inside the star. If this theory is correct, the two planets would be two large sections of the gas giant's core. According to the

Extrasolar Planets Encyclopedia The Extrasolar Planets Encyclopaedia is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995, which maintains a database of all the currently known and candidate extrasolar planets, with indi ...

, the star left the red giant stage ago.

Notes

References

{{Reflist

External links

Kepler mission planet discoveries
C Exoplanets discovered in 2011 Exoplanets discovered by the Kepler space telescope Cygnus (constellation)

Origins

See also

Notes

References

External links