V391 Pegasi b, also known as HS 2201+2610 b, is an

extrasolar planet 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 ...

candidate orbiting the star

V391 Pegasi V391 Pegasi, also catalogued as HS 2201+2610, is a blue-white subdwarf star approximately 4,000 light-years away in the constellation of Pegasus. The star is classified as an "extreme horizontal branch star". It is small, with only h ...

approximately 4,570 light-years away in the constellation of Pegasus. The candidate

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

was discovered by means of variable star timing, which measured anomalies in variability of the star caused by a planet. It is the first planet candidate to claim to be detected with this method. The discovery reported the planet candidate to have

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...

of 3.2 times

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...

's (assuming an edge-on orbit), semi-major axis of 1.7 AU, and

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 1,170 days. The planet candidate was discovered in March 2007 and published in September 2007. If it is confirmed, its survival would indicate that planets at

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

-like distances can survive their star's red-giant phase, though this is a much larger planet than Earth (about the same size as Jupiter and Saturn). Its existence has been called into question with further monitoring of the pulsations of the star which show deviations from the predicted behavior if this were in fact a planet. The variations in the pulsations may be due to unknown stellar variability.

References

* *

External links

The Extrasolar Planets Encyclopaedia: Notes for planet V391 Pegasi b
Pegasus (constellation) Giant planets Exoplanets discovered in 2007 Exoplanets detected by timing {{extrasolar-planet-stub