Kepler-70
22.9 ± 3.1 L ☉
KOI -55 ( KIC also KPD 1943 4058 05,807,616 or ) is a star in the constellation Cygnus with an apparent visual magnitude of 14.9 like in a distance of about 3800 light years. It is a hot B subdwarf, who has finished his phase as a red giant before around 18 million years ago. The star is probably surrounded by at least two planets.
Planetary system
In 2011, two planets were discovered in a very close orbit around the star. The two planets KOI -55 b and KOI -55 c [NB 1] have masses of probably less than a mass of earth and orbiting it in only 5.76 or 8.23 hours in a ( projected ) distance of 0.0060 or 0.0076 AU. The planets were detected in data from the Kepler space telescope indirectly by variations in the pulsation period of the star, the brightness changes of less than 0.01 % are caused by light reflected from the planet starlight.
The two planets are remarkable in that they are likely to have the red giant phase of the star actually did not survive. The current models, according to planets orbiting their stars in less than about 1 AU, swallowed by him when he blows up into a red giant.
According to the discoverers were KOI -55 b and 55 c KOI - gas giants like Jupiter, which have their star originally encircled on further outward tracks. As the star is a red giant inflated, they were swallowed up by its shell. Thus they were slowed down and getting pulled further inward until they finally lost their gaseous envelopes. Backwardness, the observed small cores of rock. This scenario is confirmed by model calculations, according to which the predecessor of the now observed planet must have had masses of about one Jupiter mass.
Possibly also the development of the star was affected by the operation. Hot subdwarfs are stars that burn helium in the core and have only a very thin shell of hydrogen. Normally, helium is fused from Red Giant, which are surrounded by a massive hydrogen envelope. Hot subdwarfs would be the cores of red giants that have lost their shell. This happens in close interacting binary star systems in which the companion orbital angular momentum to the envelope of the red giant, which is thereby accelerated and can be replaced. However, many hot sub- dwarfs, as well as KOI -55, single stars. In this case, instead of a stellar companion could the planet have caused the replacement of the shell.
It can not be excluded that the two planets are no remnants of the original system, but have only then newly formed from the cast-off material from the star. It is doubtful whether the time would have been enough of 18 million years for it. In another scenario, the two planets are fragments of a single, larger gas planet that was swallowed by the envelope of the red giant and eventually torn apart by the tidal forces of the star.