Fast Radio Bursts
A five-millisecond flash hidden in Parkes Observatory data from 24 July 2001 opened the case: fast radio bursts are now found in galaxies far beyond the Milky Way, with repeaters such as FRB 121102 firing from a dwarf galaxy while other sources leave only one pulse behind; the 2020 burst from the Galactic magnetar SGR 1935+2154 showed that highly magnetized dead stars can produce FRB-like blasts, yet the different host galaxies, rhythms, energies, and silences keep raising the harder question, whether one cosmic engine is responsible or several are hiding behind the same millisecond scream.
Fast radio bursts entered astronomy through a hidden trace in old data. In 2007, Duncan Lorimer, David Narkevic, Maura McLaughlin, Matthew Bailes, and Fronefield Crawford reported a bright millisecond radio pulse found in archival observations from the Parkes radio telescope in New South Wales, Australia. The signal itself had been recorded on 24 July 2001 during a survey of the Magellanic Clouds. It was short, less than five milliseconds, but extraordinarily bright, with a frequency-dependent delay that closely matched the dispersion expected from radio waves passing through ionized plasma across a long cosmic path. The event became known as the Lorimer burst, later catalogued as FRB 010724.
At first, even the basic nature of the burst was uncertain. Radio astronomers are trained to be cautious because terrestrial radio-frequency interference can imitate celestial signals. Parkes later recorded strange swept-frequency events called perytons, and these cast doubt over the earliest FRB interpretation. That caution proved scientifically valuable. In 2015, Emily Petroff and colleagues traced Parkes perytons to microwave ovens at the observatory, specifically radio emission escaping when a microwave door was opened prematurely during magnetron shutdown. The same study argued that FRB 010724 could not be explained by those ovens and remained distinct from the terrestrial perytons. The case therefore developed in two layers: a real astrophysical class of burst, and a separate lesson in how earthly interference can mimic cosmic mystery.
The field moved from suspicion to a recognized population as more bursts were discovered. In 2013, Thornton and colleagues reported several more high-latitude Parkes bursts, strengthening the case that FRBs were not a single instrumental accident. In 2014, FRB 121102 was found in Arecibo Observatory data, an important step because it came from a different telescope and geographic location. In 2016, FRB 121102 was shown to repeat. That discovery ruled out models that require every FRB to destroy its source, at least for that one object. In 2017, radio interferometry localized FRB 121102 to a faint dwarf galaxy at cosmological distance and close to a persistent radio source, proving that at least some FRBs are extragalactic and enormously energetic.
The mystery changed shape after localization became possible. The Australian Square Kilometre Array Pathfinder localized the apparently non-repeating FRB 180924 to a massive galaxy at redshift 0.3214, showing that not all well-studied FRBs live in the same kind of environment as FRB 121102. The Canadian Hydrogen Intensity Mapping Experiment, or CHIME, then transformed the field with a wide field of view and hundreds to thousands of detections. CHIME catalogues have shown that repeaters and apparent one-off sources overlap in some properties but differ in others, such as burst width and bandwidth. As of the second CHIME/FRB catalogue, thousands of bursts and thousands of unique sources have been processed under a common survey framework, yet the physical engine remains debated.
A crucial clue arrived from inside the Milky Way. On 28 April 2020, the Galactic magnetar SGR 1935+2154 produced a bright radio burst seen by CHIME/FRB and STARE2 in association with high-energy activity. NASA and the observing teams described it as the first FRB-like burst seen from within our own galaxy. This linked magnetars, highly magnetized neutron stars, directly to at least some FRB-like radio bursts. It did not close the case entirely. Extragalactic FRBs span a wide range of brightness, repetition behavior, host environments, polarization, durations, and local conditions. Magnetars are now a leading explanation, but whether they explain all FRBs, and exactly how coherent radio emission is generated, remains unresolved.
Fast radio bursts are therefore not mysterious because scientists doubt they exist. They are officially documented astrophysical events, observed by many instruments and catalogued in international systems. Their mystery lies in the mechanism. What kind of compact object can release such brief, bright radio flashes? Why do some sources repeat while many have not repeated during observing campaigns? Are apparent one-off bursts truly non-repeating, or only rarely active? How much of the observed diversity comes from the engine itself and how much from plasma near the source or along the line of sight? FRBs have also become tools: their dispersion can trace otherwise invisible matter between galaxies. A discovery that began as a strange streak in old Parkes data is now a major branch of time-domain astrophysics, still open, still accelerating, and still not fully explained.