Fast radio bursts
Transient radio bursts of unknown high-energy astrophysical origin.
Fast radio bursts (FRBs) are transient radio waves in radio astronomy, lasting from a fraction of a millisecond to 3 seconds, caused by a high-energy astrophysical process not yet understood. Their exact origin remains under investigation, with proposals ranging from rapidly rotating neutron stars and black holes to extraterrestrial intelligence. The first such burst, known as the Lorimer burst, was identified in 2007 by Duncan Lorimer and his student David Narkevic while examining archival data from a pulsar survey, recorded in 2001. Since then, numerous FRBs have been detected, including several that repeat in seemingly irregular patterns; only one, FRB 180916, has been observed to pulse with a regular period of 16.35 days. While most FRBs originate outside the Milky Way, the first galactic burst was recorded by the CHIME radio telescope in April 2020. In a single year, over 500 FRBs from outer space were detected. When polarized, the signals indicate an origin within an extremely powerful magnetic field. A major breakthrough came in April 2020 with the detection of FRB 200428, a pair of millisecond bursts from the same region as the magnetar SGR 1935+2154. Though intrinsically thousands of times less bright than typical extragalactic FRBs, its proximity made it the most powerful FRB observed, establishing magnetars as at least one source. Further studies support this link. In 2024, research on FRB 20201124A, a persistent FRB about 1.3 billion light-years away, suggested its origin in a binary system with a high accretion rate, blowing a plasma bubble responsible for the persistent radio emission. The bursts themselves are bright, broadband, millisecond flashes appearing as single spikes of energy, detected across the sky and not concentrated along the Milky Way’s plane.
- typical_duration
- Fraction of a millisecond to 3 seconds
- energy_comparison
- As much energy in a millisecond as the Sun in three days
- confirmed_source_type
- Magnetars (at least one ultimate source)
Lore & Background
Fast radio bursts are transient radio emissions lasting from a fraction of a millisecond to three seconds, caused by an unknown high-energy astrophysical process. At their source, they are extremely energetic, releasing as much energy in a millisecond as the Sun emits in three days, yet the signal reaching Earth is vastly weaker. The bursts appear as bright, unresolved, broadband spikes of energy that stand out from the background noise, typically lasting only milliseconds. They are observed across the sky and are not concentrated along the plane of the Milky Way, indicating most originate outside our galaxy. The first detected burst, found in archival data from 2001 and described in 2007, is known as the Lorimer burst. Many subsequent bursts have been recorded, including some that repeat irregularly; only one has been observed to repeat with a regular period of about 16.35 days. The first Milky Way FRB was detected in April 2020. When polarized, these signals suggest an origin within an extremely powerful magnetic field. Proposed sources include rapidly rotating neutron stars, black holes, and magnetars. One burst detected in 2020 from within our galaxy was linked to a known magnetar, establishing magnetars as at least one ultimate source, though the exact cause remains unclear. In 2024, a study of a persistent FRB located about 1.3 billion light-years away suggested it originates in a binary system with a high accretion rate, blowing a plasma bubble responsible for the persistent radio emission.
Reader's Guide
Fast radio bursts are transient radio pulses lasting from under a millisecond to three seconds, originating from high-energy astrophysical processes not yet understood. The first such burst, the Lorimer burst, was discovered in 2007 while examining archival pulsar survey data. Most bursts are extragalactic, though the first within the Milky Way was detected in April 2020. Some bursts repeat irregularly, while one, FRB 180916, pulses regularly every 16.35 days. When polarized, these signals indicate emission from a source within an extremely powerful magnetic field. Proposed origins include rapidly rotating neutron stars, black holes, or magnetars. In 2020, a pair of millisecond bursts from the magnetar SGR 1935+2154 within our galaxy established magnetars as at least one ultimate source, though the exact cause remains unknown. The first repeating source, FRB 121102, was localized in 2017 to a galaxy three billion light-years away in an extreme environment, while a non-repeating burst, FRB 180924, was traced to a larger, more ordinary galaxy. In 2024, research on FRB 20201124A, one of two known persistent bursts, suggested its origin in a binary system with a high accretion rate that blows a plasma bubble, immersed in a star-forming region. These bursts serve as tools to probe extreme environments and exotic objects, with implications for understanding the universe’s most energetic processes.
The Accidental Discovery and Early Years
The story of fast radio bursts began not with a targeted search but with a serendipitous find. For years afterward, most detections came from re-examining old recordings rather than catching events as they happened.
An Enormous Energy in a Blink
Despite their brevity, fast radio bursts pack a staggering energy budget. Astronomers estimate that a typical FRB unleashes in roughly a millisecond as much power as our Sun radiates over three full days. Yet by the time that signal traverses intergalactic space and reaches Earth, it arrives extraordinarily faint—described as a thousand times weaker than a mobile phone signal beamed from the Moon. The bursts themselves are broadband, spanning a wide range of radio frequencies, and appear as single, unresolved spikes of energy with no noticeable change in intensity over their duration. They typically last from a fraction of a millisecond up to about three seconds. A distinctive fingerprint of each burst is its dispersion measure: longer wavelengths arrive slightly later than shorter ones because free electrons in the interstellar medium slow them by different amounts, producing a rapid downward frequency sweep in the received signal. When polarization is detected, it reveals the emission originated inside an extraordinarily strong magnetic field.
Hunting for the Source
Pinpointing what actually produces an FRB has been one of radio astronomy's most persistent puzzles. Proposals have ranged from rapidly spinning neutron stars and black holes to, more speculatively, extraterrestrial intelligence. Although intrinsically thousands of times dimmer than extragalactic FRBs, its proximity within our own galaxy made it the brightest FRB ever measured, with peak flux comparable to famous radio sources like Cassiopeia A and Cygnus A. This firmly established magnetars as at least one class of FRB producer.
A Rapidly Growing Census
The catalog of known fast radio bursts has exploded in the past decade. These discoveries collectively demonstrate that FRBs are neither rare nor confined to a single type of environment.
Frequently Asked Questions
How long do Fast radio bursts last?
A typical burst fires for anywhere between a fraction of a millisecond and roughly three seconds, making them some of the shortest energetic transients detectable from beyond the Milky Way.
How energetic are Fast radio bursts compared to the Sun?
At their source, a single burst can release as much energy in one millisecond as our Sun radiates over about three days. By the time the signal reaches Earth, however, it has weakened to roughly a thousandth the strength of a cell phone perched on the Moon.
Could Fast radio bursts be signals from extraterrestrial intelligence?
The idea has been raised as one possibility among many, but the most widely discussed explanations still point to natural sources such as rapidly spinning neutron stars or activity near black holes. No burst has been confirmed as artificial to date.
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