Extrasolar planets

Main article: Extrasolar planet.
Most extrasolar planets (those outside our solar system) discovered to date have masses which are about the same or larger than Jupiter's.

Exceptions include at least planets discovered orbiting PSR B1257+12 a burned-out star, or supernova remnant, called a pulsar, comparable in size to the terrestrial planets; planets orbiting the stars Mu Arae, 55 Cancri and GJ 436 which are approximately Neptune-sized [3]; and a planet orbiting Gliese 876 that is estimated to be about 6 to 8 times as massive as the earth and is probably rocky in origin.

It is far from clear if the newly discovered large planets would resemble gas giants in our solar system or if they are of an entirely different type or types which are unknown in our solar system, like ammonia giants or carbon planets. In particular, some of the newly discovered planets, known as hot Jupiters, orbit extremely close to their parent star, in nearly circular orbits. They therefore receive much more stellar radiation than the gas giants in our solar system, which makes it questionable whether they are the same type of planet at all. There is also a class of hot Jupiters that orbit so close to their star that their atmospheres are slowly blown away in a comet-like tail: the Chthonian planets.

The National Aeronautics and Space Administration of the United States has a program underway to develop a Terrestrial Planet Finder artificial satellite, which would be capable of detecting the planets with masses comparable to terrestrial planets. The frequency of occurrence of these planets is one of the variables in the Drake equation which estimates the number of intelligent, communicating civilizations that exist in our galaxy.

Astronomers have recently [4] [5] detected a planet in a triple star system, a finding that challenges current theories of planetary formation. The planet, a gas giant slightly larger than Jupiter, orbits the main star of the HD 188753 system, in the constellation Cygnus, and is hence known as HD 188753 Ab. The stellar trio (yellow, orange, and red) is about 149 light-years from Earth. The planet, which is at least 14% larger than Jupiter, orbits the main star (HD 188753 A) once every 80 hours or so (3.3 days), at a distance of about 8 Gm, a twentieth of the distance between Earth and the Sun. The other two stars whirl tightly around each other in 156 days, and circle the main star every 25.7 years at a distance from the main star that would put them between Saturn and Uranus in our own Solar System. The latter stars invalidate the leading hot Jupiter formation theory, which holds these planets form at "normal" distances and then migrate inward through some debatable mechanism. This could not have occurred here, the outer star pair disrupting outer planet formation.

Interstellar planets are rogues in interstellar space, not gravitationally linked to any given solar system. No interstellar planet is known to date, but their existence is considered a plausible hypothesis on the grounds that the results of computer simulations of the origin and evolution of planetary systems often include the formation and subsequent ejection of bodies of significant mass.

Such objects are not considered among the "extra solar planets" as the International Astronomical Union ruled that any definition of a planet must include a rule that "Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed)."

Current technology is not sensitive enough to detect most planets of relatively small mass and orbiting far because such planets cause a very small "wobble effect" on their star although one measured as being one fifth the mass of Pluto was discovered around a pulsar star. It was discounted as a planet as it was a part of the Pluto controversy and anyhow now as a part of a belt of debris something which in and of itself is controversial for planet status in the International Astronomical Union is deprived of "planet" status also on those grounds. A further problem is also how a belt is now defined. Due to the Pluto controversy anything outside of the orbit of Neptune and if one doesn't include Pluto as certainly the IAU does not the orbit of Pluto is a Trans-Neptunian object a "TNO." By IAU terminology anything considered a TNO is not a Planet. Defining a Trans-Neptunian object belt at least works for planetoids with orbits that intersect but this doesn't take care of Sedna which has an orbit placing it outside of any known belt within the TNO area. Discoveries of smaller than most relatively small mass planets will require radical improvements in telescopes.

Main Paul1 Paul2 solar1 solar2 solar3 solar4 solar5

membrane filtration water distillers | yacht charter | oil painting reproductions | Safety Glasses | Night Vision | hawaiian music aloha shirts | Health Care | football shirts | oil paintings | Nashville Real Estate free credit report | Dental Care | caribbean yacht charter | south pacific yacht charter | Kit Car