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Geminga
Geminga is a neutron star approximately 250 parsecs〔 (around 800 light years) from the Sun in the constellation Gemini. Its name is both a contraction of "Gemini gamma-ray source", and a transcription of the words ''gh'è minga'' "it's not there" in the Lombard dialect of Milan (pronounced (:ɡɛˈmiŋɡa)).〔G. F. Bignami ''et al.'' An identification for ’Geminga’ (2CG 195+04) 1E 0630+178 - A unique object in the error box of the high-energy gamma-ray source. ApJ, 72:L9–L13, September 1983〕
== Pulsar ==
The nature of Geminga was quite unknown for 20 years after its discovery by NASA's Second Small Astronomy Satellite (SAS-2). Finally, in March 1991 the ROSAT satellite detected a periodicity of 0.237 seconds in soft x-ray emission. Thus, it is supposed that Geminga is a sort of neutron star: the decaying core of a massive star that exploded as a supernova about 300,000 years ago.〔(Geminga ), Internet Encyclopedia of Science〕
It was once thought that this nearby explosion was responsible for the low density of the interstellar medium in the immediate vicinity of the Solar System. This low-density area is known as the Local Bubble. Possible evidence for this includes findings by the Arecibo Observatory that local micrometre-sized interstellar meteor particles appear to originate from its direction.〔(【引用サイトリンク】 title=The Sun's Exotic Neighborhood )〕 More recently, however, it has been suggested that multiple supernovae in subgroup B1 of the Pleiades moving group were more likely responsible, becoming a remnant supershell.
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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