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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, over 400 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 with indirect methods, such as Doppler spectroscopy (determining the "wobble" of the parent star due to the orbiting planet's gravitational tug) or transit photometry (measuring the ever-so-slight dimming of the parent star when the planet passes through the line of sight, obscuring part of the star). Actually phtographing the planet's faint speck of light against the host star's overwhelming glare is much more challenging, yet ultimately more rewarding because it provides critical information about the planet's orbit and the temperature and composition of its atmosphere.[[File:G1758.jpg|thumb|280px|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. "B" (formally GJ758 B) has a mass of 10 to 40 times Jupiter, and is either a giant planet or a lightweight brown dwarf; its temperature is about 620oF / 327oC]]

[[File:G1758.jpg|thumb|280px|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. "B" (formally GJ758 B) has a mass of 10 to 40 times Jupiter, and is either a giant planet or a lightweight brown dwarf; its temperature is about 620oF / 327oC]]

== Methods of detection ==

== Methods of detection ==

*[http://exoplanet.eu/ Extrasolar Planets Encyclopaedia]

*[http://exoplanet.eu/ Extrasolar Planets Encyclopaedia]

*[http://exoplanets.org/ ExoPlanets]

*[http://exoplanets.org/ ExoPlanets]

 

[[category:astronomy]]

[[category:astronomy]]