Article Posted on : - Jan 09, 2010

Artist's rendition of CoRoT-7b's surface, in close orbit around its parent star. ESO / L. Calcada Photo.

LONDON (PTI): Corot-7b, the smallest-known planet outside our solar system, probably was a Saturn-sized "gas giant" planet, American scientists suggest.

According to a research presented at the 215th American Astronomical Society meeting, the planet, with diameter 70 per cent larger than that of the earth, has had much of its mass boiled away by the star's heat.

Using a computer model, the team estimated that the planet, which orbits at one-sixtieth the distance from the earth to the sun, once orbited at a distance 50 per cent higher than its current one, and had about 100 times as much mass as earth.

The team opined that as mass was burned off, the tides on its star changed, resulting in bringing the planet closer to the star. As it drew in closer, surface temperatures rose, driving off more mass, BBC reported.

The researchers reckoned that if Corot-7b's orbit is not exactly circular, then it is a hotbed of volcanic activity.

"The planet may be volcanically active if its orbit is even slightly elliptical, rather than circular," said Rory Barnes of the University of Washington.

The shifting gravity that Corot-7b -- spotted by the French space-based telescope Corot -- would experience as it moved nearer to and farther from the star in its 20-hour orbit would stretch and squash the planet mercilessly. This would drive friction in it's interior and volcanoes on it's surface.

"If conditions are what we speculate, then Corot-7b could have multiple volcanoes going off continuously and magma flowing all over the surface," Barnes said.