In radio astronomy, a fast radio burst (FRB) is a transient radio pulse of length ranging from a fraction of a millisecond, for an ultra-fast radio burst,[2][3] to 3 seconds,[4] caused by some high-energy astrophysical process not yet understood. Astronomers estimate the average FRB releases as much energy in a millisecond as the Sun puts out in three days.[5] While extremely energetic at their source, the strength of the signal reaching Earth has been described as 1,000 times less than from a mobile phone on the Moon.[6]
The first FRB was discovered by Duncan Lorimer and his student David Narkevic in 2007 when they were looking through archival pulsar survey data, and it is therefore commonly referred to as the Lorimer Burst.[7][8] Many FRBs have since been recorded, including several that have been detected to repeat in seemingly irregular ways.[9][10][11][12][13] Only one FRB has been detected to repeat in a regular way: FRB 180916 seems to pulse every 16.35 days.[14][15]
Most FRBs are extragalactic, but the first Milky Way FRB was detected by the CHIME radio telescope in April 2020.[16] In June 2021, astronomers reported over 500 FRBs from outer space detected in one year.[17]
When the FRBs are polarized, it indicates that they are emitted from a source contained within an extremely powerful magnetic field.[18] The exact origin and cause of the FRBs is still the subject of investigation; proposals for their origin range from a rapidly rotating neutron star and a black hole, to extraterrestrial intelligence.[19][20] In 2020, astronomers reported narrowing down a source of fast radio bursts, which may now plausibly include "compact-object mergers and magnetars arising from normal core collapse supernovae".[21][22][23] A neutron star has been proposed as the origin of an unusual FRB with periodic peaks lasting over 3 seconds reported in 2022.[24]
The discovery in 2012 of the first repeating source, FRB 121102, and its localization and characterization in 2017, has improved the understanding of the source class. FRB 121102 is identified with a galaxy at a distance of approximately three billion light-years and is embedded in an extreme environment.[25][18] The first host galaxy identified for a non-repeating burst, FRB 180924, was identified in 2019 and is a much larger and more ordinary galaxy, nearly the size of the Milky Way. In August 2019, astronomers reported the detection of eight more repeating FRB signals.[26][27] In January 2020, astronomers reported the precise location of a second repeating burst, FRB 180916.[28][29] One FRB seems to have been in the same location as a known gamma-ray burst.[30][16]
On 28 April 2020, a pair of millisecond-timescale bursts (FRB 200428) consistent with observed fast radio bursts, with a fluence of >1.5 million Jy ms, was detected from the same area of sky as the magnetar SGR 1935+2154.[31][32] Although it was thousands of times less intrinsically bright than previously observed fast radio bursts, its comparative proximity rendered it the most powerful fast radio burst yet observed, reaching a peak flux of either a few thousand or several hundred thousand janskys, comparable to the brightness of the radio sources Cassiopeia A and Cygnus A at the same frequencies. This established magnetars as, at least, one ultimate source of fast radio bursts,[33][34][35] although the exact cause remains unknown.[36][37][38] Further studies support the notion that magnetars may be closely associated with FRBs.[39][40] On 13 October 2021, astronomers reported the detection of hundreds of FRBs from a single system.[41][42]
