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GRB 101225A, also known as the "Christmas burst", was a cosmic explosion first detected by NASA's Swift observatory on Christmas Day 2010. The gamma-ray emission lasted at least 28 minutes, which is unusually long. Follow-up observations of the burst's afterglow by the Hubble Space Telescope and ground-based observatories were unable to determine the object's distance using spectroscopic methods. In papers published in the journal ''Nature'', two different groups of astronomers proposed different theories about the event's origin. Sergio Campana's group proposes that the event was caused by a comet crashing onto a neutron star within our own galaxy. Christina Thöne's group prefers a more conventional supernova mechanism, involving a merger between a helium star and a neutron star at a distance of about 5.5 billion light years from Earth. == Observations == The gamma ray burst, in the constellation Andromeda, was first detected by the NASA Swift Gamma-Ray Burst Mission at 18:38 UT on December 25, 2010. The gamma-ray emission had a duration of at least 28 minutes, which is unusually long. After news of the gamma-ray burst was sent to other observatories, the longer-wavelength "afterglow" of the burst was monitored by on-ground observatories and the Hubble Space Telescope.〔 After the unusually long duration of gamma emissions, x-ray emissions in the afterglow continued for just two days, an unusually short duration for this phase.〔 Optical emissions observed over the first 10 days were characterized as those of "an expanding, cooling blackbody with a large initial radius". A faint light source appeared about 10 days after the burst and reached its maximum brightness 30 days after its appearance; observers described this light source as looking like a supernova.〔(【引用サイトリンク】 title=Cosmic Explosion Explained Just in Time for Christmas; Texas-Korea Astronomical Partnership Contributes )〕 On January 6, 2011, the 10m Keck-I telescope equipped with the Low Resolution Imaging Spectrometer (LRIS) conducted spectroscopic measurements of the host galaxy of GRB 101225A. A 900s spectrum was obtained; it consisted of blue and red channels, covering the wavelength ranges ~320–550 nm and ~500–820 nm, respectively. Isotropic energy was estimated at (7.8 ± 1.6) erg from the Burst Alert Telescope (BAT) data. The unusual characteristics of the afterglow led astronomers to generate novel hypotheses to explain the event. Observers were unable to ascertain the burst's distance from Earth, and the two alternative hypotheses of its origin place the event at radically different distances.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「GRB 101225A」の詳細全文を読む スポンサード リンク
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