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PSR B1257+12 A
PSR B1257+12 b (ex PSR B1257+12 A) is an exoplanet (or extrasolar planet) approximately 980 light-years away in the constellation of Virgo. The planet is the innermost object orbiting the pulsar PSR B1257+12, i.e. a pulsar planet in the dead stellar system. It is about twice as massive as the Moon, and is listed as the least massive planet known, including among the planets in the Solar System.
==Name==
The planets of PSR B1257+12 are designated from A to D (ordered by increasing distance). The reason that these planets are not named the same as other extrasolar planets is mainly because of time. Being the first extrasolar planets discovered, and being discovered around a pulsar, the planets were given the uppercase letters "B" and "C" (like other planets). When a third planet was discovered around the system (in a closer orbit than the other two), the name "A" was commonly used. The extrasolar planet name 51 Pegasi b (the first planet found around a Sun-like star), was the idea used for naming planets. Although these pulsar planets were not officially renamed, some have done it themselves. PSR B1257+12 A is catalogued as "PSR 1257+12 b" on The Extrasolar Planets Encyclopaedia.
The planet and its host star is one of the planetary systems selected by the International Astronomical Union as part of their public process for giving proper names to exoplanets and their host star (where no proper name already exists).〔(NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars ). IAU.org. 9 July 2014〕〔(NameExoWorlds ).〕 The process involves public nomination and voting for the new names, and the IAU plans to announce the new names in mid-November 2015.〔(NameExoWorlds ).〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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