Gamma-ray burst

For bursts of gamma rays of terrestrial origin, see Terrestrial gamma-ray flash.
Artist's illustration showing the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a black hole. Theoretically, energy may be released during the collapse along the axis of rotation to form a GRB.

In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies, being the brightest and most extreme explosive events in the entire universe,[1][2][3] as NASA describes the bursts as the "most powerful class of explosions in the universe".[4] They are the most energetic and luminous electromagnetic events since the Big Bang.[5][6] Gamma-ray bursts can last from ten milliseconds to several hours.[7][8] After the initial flash of gamma rays, an "afterglow" is emitted, which is longer lived and usually emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and radio).[9]

The intense radiation of most observed GRBs is thought to be released during a supernova or superluminous supernova as a high-mass star implodes to form a neutron star or a black hole. A subclass of GRBs appears to originate from the merger of binary neutron stars.[10]

The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime)[11] and extremely rare (a few per galaxy per million years[12]). All observed GRBs have originated from outside the Milky Way galaxy, although a related class of phenomena, soft gamma repeaters, are associated with magnetars within the Milky Way. It has been hypothesized that a gamma-ray burst in the Milky Way, pointing directly towards the Earth, could cause a mass extinction event.[13] The Late Ordovician mass extinction has been hypothesised by some researchers to have occurred as a result of such a gamma-ray burst.[14][15][16]

GRBs were first detected in 1967 by the Vela satellites, which had been designed to detect covert nuclear weapons tests; after thorough analysis, this was published in 1973.[17] Following their discovery, hundreds of theoretical models were proposed to explain these bursts, such as collisions between comets and neutron stars.[18] 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 redshifts using optical spectroscopy, and thus their distances and energy outputs. These discoveries, and subsequent studies of the galaxies and supernovae associated with the bursts, clarified the distance and luminosity of GRBs, definitively placing them in distant galaxies.

  1. ^ Gehrels, Neil; Mészáros, Péter (2012-08-24). "Gamma-Ray Bursts". Science. 337 (6097): 932–936. arXiv:1208.6522. Bibcode:2012Sci...337..932G. doi:10.1126/science.1216793. ISSN 0036-8075. PMID 22923573.
  2. ^ Misra, Kuntal; Ghosh, Ankur; Resmi, L. (2023). "The Detection of Very High Energy Photons in Gamma Ray Bursts" (PDF). Physics News. 53. Tata Institute of Fundamental Research: 42–45.
  3. ^ NASA Universe Web Team (2023-06-09). "Gamma-Ray Bursts: Black Hole Birth Announcements". science.nasa.gov. Retrieved 2024-05-18.
  4. ^ Reddy, Francis (2023-03-28). "NASA Missions Study What May Be a 1-In-10,000-Year Gamma-ray Burst - NASA". nasa.gov. Retrieved 2023-09-29.
  5. ^ "Gamma Rays". NASA. Archived from the original on 2012-05-02.
  6. ^ Zhang, Bing (2018). The Physics of Gamma-Ray Bursts. Cambridge University Press. pp. xv, 2. ISBN 978-1-107-02761-9.
  7. ^ Atkinson, Nancy (2013-04-16). "New Kind of Gamma Ray Burst is Ultra Long-Lasting". Universe Today. Retrieved 2022-01-03.
  8. ^ Cite error: The named reference Kouveliotou was invoked but never defined (see the help page).
  9. ^ Vedrenne & Atteia 2009
  10. ^ Cite error: The named reference PhysRev was invoked but never defined (see the help page).
  11. ^ Arizona State University (26 July 2017). "Massive star's dying blast caught by rapid-response telescopes". PhysOrg. Retrieved 27 July 2017.
  12. ^ Podsiadlowski 2004
  13. ^ Melott 2004
  14. ^ Melott, A.L. & Thomas, B.C. (2009). "Late Ordovician geographic patterns of extinction compared with simulations of astrophysical ionizing radiation damage". Paleobiology. 35 (3): 311–320. arXiv:0809.0899. Bibcode:2009Pbio...35..311M. doi:10.1666/0094-8373-35.3.311. S2CID 11942132.
  15. ^ Cite error: The named reference renamed_from_2021_on_20231204051223 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference TerrestrialOzoneDepletion was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference KSO was invoked but never defined (see the help page).
  18. ^ Hurley 2003