Extrasolar planet - Wikipedia

http://en.wikipedia.org/wiki/Extrasolar_planet

It's fun to notice the embarrassment of the author when mentioning the existence of "Planetary Mass Objects". The restrictive definition of a planet leads scientists to find weird words for simple things. If an "object" - that looks like a planet - is not orbiting a star, it is forbidden to call them "planets". Sorry for them.

Sailom

An extrasolar planet, or exoplanet, is a planet beyond the Solar System (i.e., orbits a star other than the Sun.) As of 11 November 2006, 209 extrasolar planets have been discovered (see list of stars with known extrasolar planets).^[1]

Known exoplanets are members of planetary systems that orbit a star. There have also been unconfirmed reports of free-floating planetary-mass objects ("rogue planets": that is, ones that do not orbit any star). Since such objects do not satisfy the working definition of "planet" adopted by the International Astronomical Union, and since their existence remains unconfirmed, they will not be discussed in this article.^[2] For more information, see interstellar planet.

Infrared image of 2M1207 (blue) and its planet 2M1207b, as viewed by the Very Large Telescope. As of September 2006 this is the only confirmed extrasolar planet to have been directly imaged.

Extrasolar planets became a subject of scientific investigation in the mid-19th century. Astronomers generally supposed that some existed, but it was a mystery how common they were and how similar they were to the planets of the Solar System. The first confirmed detections were finally made in the 1990s; since 2002, more than twenty have been discovered every year. It is now estimated that at least 10% of sunlike stars have planets, and the true proportion may be much higher.^[3] The discovery of extrasolar planets raises the question of whether some might support extraterrestrial life.^[4]