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[[File:G1758.jpg|thumb|250px||right|The first photo taken of an exoplanet, by the Japanese "Subaru" telescope, August, 2009. Point "B", numbered GJ758 B, has a mass of 10 to 40 times Jupiter, and orbits a star 50 light years from Earth. Point "C" (GJ758 C) is undetermined<ref>http://www.space.com/7629-photo-object-sun-star-scientists.html</ref>.]]
'''Extrasolar planets''', or '''exoplanets''', are planets that orbit stars other than the sun. The search for them is one of the most exciting phases of astronomy today.
'''Extrasolar planets''', or '''exoplanets''', are planets that orbit stars other than the sun. The search for them is one of the most exciting phases of astronomy today.
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 photographing 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 620°F / 327°C]]
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 photographing 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.
== Methods of detection ==
== Methods of detection ==