Gamma-ray burst

In <a href="/facts/Gamma-ray_astronomy/s59YdwaX">gamma-ray astronomy</a>, gamma-ray bursts (GRBs) are extremely energetic events occurring in distant <a href="/facts/Galaxy/zCyUvEf7">galaxies</a> which represent the brightest and most powerful class of explosion in the universe. These extreme <a href="/facts/Electromagnetic_radiation/Ynx7ujCW">electromagnetic</a> emissions are second only to the <a href="/facts/Big_Bang/I5T1vTnv">Big Bang</a> as the most energetic and luminous phenomenon ever known. Gamma-ray bursts can last from a few milliseconds to several hours. After the initial flash of <a href="/facts/Gamma_ray/5Drf913J">gamma rays</a>, a longer-lived afterglow is emitted, usually in the longer wavelengths of <a href="/facts/X-ray/wseP79cN">X-ray</a>, <a href="/facts/Ultraviolet/kncBUqn5">ultraviolet</a>, <a href="/facts/Visible_spectrum/frPBh8o5">optical</a>, <a href="/facts/Infrared/44XdJNcc">infrared</a>, <a href="/facts/Microwave/HmVSN31Y">microwave</a> or <a href="/facts/Radio_waves/XmB6WPpF">radio</a> frequencies.
The intense radiation of most observed GRBs is thought to be released during a <a href="/facts/Supernova/Pfo2J23l">supernova</a> or <a href="/facts/Superluminous_supernova/59k11Ro9">superluminous supernova</a> as a high-mass <a href="/facts/Star/PFbd6ICx">star</a> implodes to form a <a href="/facts/Neutron_star/4enfoxBA">neutron star</a> or a <a href="/facts/Black_hole/1r2lmkcF">black hole</a>. Short-duration (sGRB) events are a subclass of GRB signals that are now known to originate from the cataclysmic <a href="/facts/Neutron_star_merger/AMLBIl3G">merger of binary neutron stars</a>.
The sources of most GRB are billions of <a href="/facts/Light_year/IGc5NdQb">light years</a> away from <a href="/facts/Earth/HLLmDfj0">Earth</a>, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the <a href="/facts/Sun/CadPCVHh">Sun</a> will in its entire 10-billion-year lifetime) and extremely rare (a few per galaxy per million years). All GRBs in recorded history have originated from outside the <a href="/facts/Milky_Way_galaxy/ulF6lccN">Milky Way galaxy</a>, although a related class of phenomena, <a href="/facts/Soft_gamma_repeater/0VryRaB8">soft gamma repeaters</a>, are associated with <a href="/facts/Magnetar/By90KFyJ">magnetars</a> within our galaxy. A gamma-ray burst in the Milky Way pointed directly at Earth would likely sterilize the planet or effect a <a href="/facts/Mass_extinction/HloJubtR">mass extinction</a>. The <a href="/facts/Late_Ordovician_mass_extinction/jLhHjlPf">Late Ordovician mass extinction</a> has been hypothesised by some researchers to have occurred as a result of such a gamma-ray burst.
GRB signals were first detected in 1967 by the <a href="/facts/Vela_(satellite)/9KtSMpuH">Vela satellites</a>, which were designed to detect <a href="/facts/Partial_Nuclear_Test_Ban_Treaty/vhF6shhg">covert nuclear weapons tests</a>; after an "exhaustive" period of analysis,: 979  this was published as academic research in 1973. Following their discovery, hundreds of theoretical models were proposed to explain these bursts, such as collisions between <a href="/facts/Comet/w34utQCd">comets</a> and <a href="/facts/Neutron_star/4enfoxBA">neutron stars</a>. Little information was available to verify these models until the 1997 detection of the first X-ray and optical afterglows and direct measurement of their <a href="/facts/Redshift/Qfl4VjDF">redshifts</a> using optical <a href="/facts/Spectroscopy/mj71FuNK">spectroscopy</a>, and thus their distances and energy outputs. These discoveries—and subsequent studies of the galaxies and <a href="/facts/Supernova/Pfo2J23l">supernovae</a> associated with the bursts—clarified the distance and <a href="/facts/Luminosity/1tdhpk9l">luminosity</a> of GRBs, definitively placing them in distant galaxies.

Gamma-ray burst open-in-new

Gamma-ray burst