User:Kepler-1229b/sandbox/Gliese 436 c

Gliese 436 c was the designation given to a putative extrasolar planet orbiting the star Gliese 436 in the constellation Leo at a distance of 33.4 light years or 10.2 parsecs from Earth. Gliese 436 c would be one of the most Earth-like planets ever discovered at the time. However simulations of this system taking into account the lack of change of intervals between transits of the inner planet Gliese 436 b suggested that its existence was unlikely and the discovery was retracted at the Transiting Planet conference in Boston, 2008.

Discovery
On January 23, 2008 astronomers including I. Ribas claimed to have found a possible second planet orbiting the star Gliese 436 by using a method called planetary perturbation of the inner planet Gliese 436 b, using a similar method using to discover Neptune from perturbations of Uranus in 1846. On Wednesday, April 9, 2008 Ribas published the exoplanetary discovery in Spain, by observing the grazing power of the inner transiting planet Gliese 436 b. The discovery was retracted on May 22, 2008.

Physical
Gliese 436 c would have been the smallest planet orbiting the main-sequence star, with a true mass of 5 earth masses, although same mass as the minimum mass for the planet Gliese 581 c. Its true mass was probably measured from its perturbation between planets b and c. Smaller exoplanets are known to be in orbit around the pulsar PSR B1257+12, including a world only 60% more massive than the Earth's moon. Based on the theory of tidal pseudo-synchronisation, Gliese 436 c was calculated to have a rotation period of 22 Earth days, which is 4 times as long as its orbital period. Due to its small mass and size, it would likely be a terrestrial planet like the inner planets of our solar system. The surface temperature of the planet would be around 500 K assuming a Venus-like albedo of 0.7 without taking the greenhouse effect of its atmosphere, if there is any, into account, so this planet would be too close to its star for a liquid water to exist on the planet’s surface.

Orbit
This planet was thought to take 5.2 earth days to orbit its parent star, close to a 2:1 resonance with the inner planet Gliese 436 b. Its semi-major axis would be 0.045 astronomical units.