Extrasolar planets refers to planets other than the planets in the solar system. Since the 1990s, the first confirmed extra solar planets exist. As of June 28, 2010 humans have discovered 464 extra solar planets. History astronomers generally believe that there are other planets outside our solar system, but the extent and nature of there general is a mystery. Until the 1990s, was first confirmed human existence of extra solar planets, but since 2002 every year more than 20 extra solar planets were newly discovered. It is estimated that less than 10% are similar to the sun, and the stars have there planet. With the discovery of extra solar planets that was extended to the existence of alien life problems.
Although all know extra solar planets are subsidiary different planetary systems, but there are some reports that there may be any stars that do not focus on revolution, but has a planetary mass because the International Astronomical Union is not whether such objects have defined the planet but has not yet confirmed the existence of such objects, so this will not be addressed in such objects. The content can be found in interstellar planets. Most of the known extra solar planets are around, and the sun like stars that stellar spectra for the F, G or K for main sequence stars. One of the reasons is the search for such programs tend to focus on the stars.
According to International Astronomical Union the definition of planet is to revolve around a star. However, this definition applies only to planets inside the solar system. All extra solar planets have been excluded. This 2001 International Astronomical Union for extra solar planets in the following definition, “Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extra solar object to be considered a planet should be the...