Extrasolar Planet

An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of 851 such planets (in 670 planetary systems, including 126 multiple planetary systems) have been identified as of November 19, 2012, all of them within the Milky Way galaxy. It is expected that there are many billions of planets in the Milky Way galaxy, not only occurring around stars but also as free-floating planetary-mass bodies The nearest known exoplanet is Alpha Centauri Bb.

For centuries, many philosophers and scientists supposed that extrasolar planets existed, but there was no way of knowing how common they were or how similar they might be to the planets of the Solar System. Various detection claims made starting in the nineteenth century were all eventually rejected by astronomers. The first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmed detection of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Due to improved observational techniques, the rate of detections has increased rapidly since then. Some exoplanets have been directly imaged by telescopes, but the vast majority have been detected through indirect methods such as radial velocity measurements.

Most known exoplanets are giant planets believed to resemble Jupiter or Neptune, but this reflects a sampling bias, as massive planets are more easily observed. Some relatively lightweight exoplanets, only a few times more massive than Earth (now known by the term Super-Earth), are known as well; statistical studies now indicate that they actually outnumber giant planets while recent discoveries have included Earth-sized and smaller planets and a handful that appear to exhibit other Earth-like properties. There also exist planetary-mass objects that orbit brown dwarfs and other bodies that "float free" in space not bound to any star; however, the term "planet" is not always applied to these objects.

The discovery of extrasolar planets, particularly those that orbit in the habitable zone where it is possible for liquid water to exist on the surface (and therefore also life), has intensified interest in the search for extraterrestrial life. Thus, the search for extrasolar planets also includes the study of planetary habitability, which considers a wide range of factors in determining an extrasolar planet's suitability for hosting life.

Read more about Extrasolar Planet:  Detection Methods, Definition, Habitability

Other articles related to "extrasolar planet, planet, planets, extrasolar":

OGLE-TR-10b
... OGLE-TR-10b is an extrasolar planet orbiting the star OGLE-TR-10 ... The planet was first detected by the Optical Gravitational Lensing Experiment (OGLE) survey in 2002 ... The planet is a typical "hot Jupiter", a planet with a mass half that of Jupiter and orbital distance only 1/24th that of Earth from the Sun ...
Extrasolar Planet - Habitability
... Several planets have orbits in their parent star's habitable zone, where it should be possible for liquid water to exist and for Earth-like conditions to prevail ... Most of those planets are giant planets more similar to Jupiter than to Earth if any of them have large moons, the moons might be a more plausible abode of life ... Discovery of Gliese 581 g, thought to be a rocky planet orbiting in the middle of its star's habitable zone, was claimed in September 2010 and, if confirmed, it could be ...
Gliese 777 B
... Gliese 777 b, also known as Gliese 777 Ab or HD 190360 b, is an extrasolar planet approximately 52 light-years away in the constellation of Cygnus ... The planet was discovered orbiting the primary star of the Gliese 777 system in June 2002 (by the Geneva Extrasolar Planet Search Team) using the radial velocity ... The planet is at least one half more massive than Jupiter but roughly the same size as Jupiter ...
Gaia Spore - Technological Challenges - Potential Gaia Progeny
... Gliese 581 c is a "super-earth" extrasolar planet orbiting the red dwarf star Gliese 581 ... It appears to be the first terrestrial extrasolar planet discovered in the hypothetical habitable zone surrounding its star, where surface temperatures might maintain liquid water ... The planet is astronomically close, at 20.4 light years (193 trillion km or 119 trillion miles) from Earth in the direction of the constellation of Libra ...
Sudarsky Extrasolar Planet Classification
... The Sudarsky extrasolar planet classification system is a theoretical model-based classification system for predicting the appearance of extrasolar gas giants based on their temperature ... paper Albedo and Reflection Spectra of Extrasolar Giant Planets and expanded on in Theoretical Spectra and Atmospheres of Extrasolar Giant Planets, published before any successful direct or ... a broad classification system with the goal of bringing some order to the likely rich variety of extrasolar gas-giant atmospheres ...

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