GRB 221009A

GRB 221009A came from the constellation of Sagitta and occurred an estimated 1.9 billion years ago,[7] however its source is now 2.4 billion light-years away from Earth due to the expansion of the universe during the time-of-flight to Earth.[8] The burst's high-intensity emissions spanned 15 orders of magnitude on the electromagnetic spectrum, from radio emissions to gamma rays. Radio signals broadcast by the winding-down of whatever process created the initial burst will likely linger for years to come.[9] This broadband emission offers the rare opportunity to study normally-fleeting GRBs in great detail.[7][9]

The burst saturated the Fermi Gamma-ray Space Telescope's detector,[10] which captured gamma ray photons with energies exceeding 100 GeV.[11] GRB 221009A is by far the most productive event for very high energy (VHE) photons ever witnessed by scientific instrumentation. Prior to GRB 221009A, the number of very high energy photons detected over the entire history of GRB astronomy numbered only a few hundred. When the burst's radiation arrived at Earth the Large High Altitude Air Shower Observatory (LHAASO) alone saw more than 5,000 such VHE photons. Some of these photons arrived at Earth carrying a record 18 TeV of energy,[12][3] more than can be produced at the Large Hadron Collider (LHC) at the European Center for Nuclear Research (CERN).[13] Russia's Carpet-2 facility at the Baksan Neutrino Observatory may have also recorded a single 251-TeV photon from this burst.[10]

GRB 221009A was subsequently observed by the Neutron Star Interior Composition Explorer (NICER),[7] the Monitor of All-sky X-ray Image (MAXI), the Imaging X-ray Polarimetry Explorer (IXPE),[14][15][16] the International Gamma-ray Astrophysics Laboratory (INTEGRAL), the XMM-Newton space telescope,[17] and many others.[13][18]

GRB 221009A may have been caused by a massive star undergoing a supernova,[3] or by the birth of a black hole.[11] Supernovae often lead to the formation of a black hole if the parent star is too massive for stable neutron star formation, and it is not yet known which part of, or whether, the death of a star was responsible for this gamma-ray burst. Some physicists speculate that the exceptionally high-energy photons observed during 221009A could be the result of previously theoretical or unknown physical processes involving dark matter,[10] axions, or decaying sterile neutrinos.[19] As yet there is no conclusive evidence that this gamma-ray burst was caused by a supernova,[20][21][22][23] nor have any of the enormous number of neutrinos emitted by supernovae been detected.[24] Lightning detectors in India and Germany picked up signs that the Earth's ionosphere was perturbed for several hours by the burst, though only mildly,[4][10][25] as well as an enormous influx of electrically charged particles.[26]

Some astronomers referred to the burst as the "brightest of all time", or by the acronym "BOAT".[10][27] This claim easily justified by the record of known gamma-ray bursts.[6] The power of gamma-ray bursts may be gauged by the degree of interaction between the gamma rays they emit and the ubiquitous lanes of interstellar dust in deep space. Such interactions generate an afterglow in X-ray frequencies, usually seen as concentric rings of scattered X-rays with the gamma ray burst at the center. GRB 221009A is only the seventh gamma-ray burst known to have generated these rings.[5] The X-ray afterglow of 221009A was hundreds of times brighter than any seen before[28] and as of June 2023 a record twenty X-ray afterglow rings have been identified around the burst.[29]

Through comparison of data collected by different observatories scientists concluded that the 221009A event was 50 to 70 times brighter than the previous record holder.[18][5] The extremely bright peak and long afterglow may help physicists study the manner in which matter interacts at relativistic speeds, the only known regime capable of generating gamma ray photons with more then 100 GeV of energy.[7] Study of 221009A and similarly extreme events are at present humanity's only access to particles with energies larger than any that can be generated artificially. The close examination of 221009A may eventually yield physical explanations that are neither predicted by nor accounted for in the Standard Model.[10]

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  Near-simultaneous observations were made of GRB221009A from Gemini South in Chile. The image is a combination of 4 exposures in I, J, H, K with two instruments taken in the morning of Friday, October 14, 2022.[30]
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  Optical afterglow of GRB 221009A imaged by amateur astronomer using remote telescope

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  Swift's X-ray image of GRB 221009A shows circular rings around the gamma-ray burst. Dust in the Milky Way scattered the x-ray emission of the gamma-ray burst, creating the rings.[31]
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  Near-infrared afterglow and host galaxy seen by Webb's NIRCam.

• List of gamma-ray bursts