What is Gamma-ray burst?
[[Image:GRB080319B illustration NASA.jpg|thumb|right|250px|Artist's illustration of a bright gamma-ray burst occurring in a star-forming region. Energy from the explosion is beamed into two narrow, oppositely-directed jets.]] '''Gamma-ray bursts''' ('''GRBs''') are flashes of [[gamma ray]]s from extremely energetic explosions. They have been seen in distant [[galaxies]]. They are the most [[Luminosity|luminous]] [[Electromagnetism|electromagnetic]] events known to occur in the [[universe]]. Bursts can last from milliseconds to several minutes, although a typical burst lasts a few seconds. The initial burst is usually followed by a longer-lived 'afterglow' emitted at longer wavelengths ([[X-ray]], [[ultraviolet]], [[visible light]], [[infrared]] and [[radio]] waves). Most GRBs are a narrow beam of intense radiation released during a [[supernova]], as a huge rapidly spinning star collapses to form a [[black hole]]. A subclass of GRBs (the 'short' bursts) seem to come from a different process, perhaps the merger of [[binary star|binary]] [[neutron]] stars. The sources of most GRBs are [[billion]]s of [[light year]]s away from [[Earth]]. This suggests the explosions are extremely energetic: a typical burst releases as much energy in a few seconds as the [[Sun]] will in its entire 10 [[billion]] year lifetime.<ref name=Frail2001>{{cite journal | author = Frail D.A. | display-authors = etal | year = 2001 | title = Beaming in Gamma-ray bursts: evidence for a standard energy reservoir | journal = Astrophysical Journal Letters | volume = 562 | issue = 1 | pages = L557–L558 | doi = 10.1086/338119 | arxiv = astro-ph/0102282 | bibcode = 2001ApJ...562L..55F | s2cid = 1047372 }}</ref> They are very rare (a few per galaxy per million years).<ref name=Pod>{{cite journal | author = Podsiadlowski, Ph. | display-authors = etal | year = 2004 | title = The rates of hypernovae and gamma-ray bursts: implications for their progenitors | journal = Astrophysical Journal Letters | volume = 607 | issue = 1 | pages = L17–