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New extrasolar planet is the smallest yet discovered |
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Written by Derek Kessler on
Tuesday, 15 April 2008
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 A relatively small rocky extrasolar planet is the smallest yet discovered by man, paving the way towards discoveries of Earth-sized and smaller globes orbiting distant stars. This planet was discovered orbiting the star GJ 436, located in the constellation Leo. It weighs in at a hefty 5 Earth masses, or 33 trillion billion tons, a size that models indicate is more likely to result in a rocky planet than the significantly larger gas giants that have dominated the list of discovered planets. The smallest gas giant in our solar system, Uranus, comes in at just over 14 Earth masses.
Named GJ 436c, after its host star, the planet is estimated to have a radius of about 9600 km, as compared to Earth’s 6400 km. It orbits GJ 436 in just 5.2 Earth days and is thought to make a complete daily rotation in 4.2 Earth days. GJ 436 is located 30 light-years from Earth.
The planet was predicted to exist from observations made on another planet discovered around GJ 436 in 2004. The “hot ice planet,” GJ 436b, orbits close in to the star and continued study of its orbit discovered perturbations that could have only been caused by another smaller planet in a wider orbit. Astronomers calculated that for every two orbits made by GJ 436b, that GJ 436c would make one.
The discovery of GJ 436c has pushed the known extrasolar planetary count closer to 300, a number that is expected to be crossed sometime this year.
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