Space Travel
11, Feb, 2012

Smallest Exoplanet Discovered
Written by spacetravel.org   
Sunday, 29 January 2006 22:10
The planet seems to orbit a red dwarf about 22,000 light-years from the Sun. The red dwarf shines so weakly compared to the Sun that the planet's surface is believed to be approximately -220°C, as cold as Pluto and Neptune

The planet was found using a technique called gravitational microlensing. When one star passes in front of another, as seen from Earth, light from the background star is gravitationally bent and magnified for a period of days to weeks. However, if the nearer star hosts a planet, the planet's gravity can further increase the background star's light for a few hours. Because the method measures only the ratio of the planet’s and star’s masses, there is some uncertainly regarding the planet’s mass, which could range from 2.8 to 11.0 Earth masses.

About 170 exoplanets have been found around normal stars.The smallest found until now weighs seven Earth masses. It was found by analysing the gravitational wobble it induced in its host star.

Since 2004, two other planets have been found with microlensing, but each was several times the mass of Jupiter.

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