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'''Extrasolar planets''', or '''exoplanets''', are planets that orbit stars other than the sun.
'''Extrasolar planets''', or '''exoplanets''', are planets that orbit stars other than the sun.
Planets have no light source of their own, and most extrasolar planets are too far away to be seen by the light they reflect from their own suns; however, some have been detected by the methods described below.
Planets have no light source of their own, and most extrasolar planets are too far away to be seen by the light they reflect from their own suns; however, over 400 have been detected by the methods described below.
[[File:G1758.jpg|thumb|The Japanese "Subaru" telescope in Aug. 2009 took one of the first photos of an exoplanet. Point "B" is an exoplanet and probably so is C.]]
== Methods of detection ==
== Methods of detection ==
== Current count ==
== Current count ==
As of 2009, the number of extrasolar planets detected stands at more than 340. Since the detection methods devised to date favor large, gaseous planets, most detected planets are quite dissimilar to Earth, and they are not thought to be good candidates for finding life. However, the planet [[Gliese_581c|Gliese 581c]] orbiting the red dwarf star Gliese 581 (approximately 20 light-years from earth) appears to be a terrestrial (that is, rocky) planet that orbits in the "habitable zone" of space surrounding its star. The term "habitable" in this context simply means that the stellar light flux it receives is similar to that of Earth, and it therefore might have an Earthlike temperature. Whether it is in fact habitable depends on many other factors, and is pure speculation at present.
As of December 2009, the number of extrasolar planets detected stands at more than 400. Since the detection methods devised to date favor large, gaseous planets, most detected planets are quite dissimilar to Earth, and they are not thought to be good candidates for finding life. However, the planet [[Gliese_581c|Gliese 581c]] orbiting the red dwarf star Gliese 581 (approximately 20 light-years from earth) appears to be a terrestrial (that is, rocky) planet that orbits in the "habitable zone" of space surrounding its star. The term "habitable" in this context simply means that the stellar light flux it receives is similar to that of Earth, and it therefore might have an Earthlike temperature. Whether it is in fact habitable depends on many other factors, and is pure speculation at present.
==See also==
==See also==