Fast Radio Burst

A Fast Radio Burst, or FRB for short, is a very brief, extremely bright burst of radio waves that reaches Earth from the universe. Radio waves are a type of invisible light — they are electromagnetic radiation, just like visible light, but with a much greater wavelength. A single burst often lasts less than a millisecond, that is, less than a thousandth of a second. In this tiny span of time, the source releases more energy than the Sun does over several days. The first FRB was discovered in 2007 in old archival data — no one had previously known what they were looking at. Since then, hundreds of further bursts have been catalogued, many of them with modern, automated telescopes.

Why FRBs are stirring up astronomy

What is special about FRBs is not only their enormous brightness, but also their origin. Most of them come from other galaxies, billions of light-years away. On this long journey, the radio waves pass through what is known as intergalactic space — the nearly empty region between galaxies. This gas between the galaxies slows different frequencies of the radio waves to different degrees, similar to how a prism splits white light into its colors. From the strength of this effect, astronomers can measure how much matter the waves have passed through on their way.

This turns FRBs into a measuring instrument for something that is otherwise barely observable: the matter between galaxies. Part of the normal matter in the universe had literally been “missing” for decades — calculations said it must exist, but telescopes could not find it. With FRBs, this missing portion was first demonstrated in 2020. This is a concrete scientific breakthrough that would not have been possible without FRBs.

From signal to discovery — how FRBs are tracked down

Radio telescopes continuously pick up signals from space. The problem: an FRB appears without warning, lasts milliseconds, and is then gone. No human could react fast enough. That is why specialized algorithms — that is, automatic computer programs — run on the telescopes' computers, searching the data stream in real time. They recognize the characteristic pattern of an FRB: a brief spike in which lower frequencies arrive slightly later than higher ones. This pattern is called dispersion.

Modern large-scale projects such as the Canadian telescope CHIME have dramatically increased the discovery rate. CHIME alone reports several FRBs per day. Machine learning helps with this: algorithms are trained to reliably distinguish genuine FRBs from interference signals — such as mobile phone signals or microwave ovens near the telescope. This is no small matter, since most signals a radio telescope receives come from human devices, not from space.

Another puzzle is repetition. Most known FRBs have shown up only once. A few, however, repeat irregularly. This suggests that there may be different types of sources — or different mechanisms that produce similar signals. The most likely source today is considered to be so-called magnetars: neutron stars with extremely strong magnetic fields that release vast amounts of energy in the form of radio waves during outbursts.

FRBs in research, technology, and media coverage

In technology news, FRBs mostly come up in connection with AI-powered astronomy. The volumes of data produced by modern radio telescopes are so large that classical evaluation methods are no longer sufficient. Neural networks — that is, AI systems that recognize patterns in data — now handle large parts of the signal search. This makes FRBs a prime example of how AI has become indispensable not only in business, but also in basic research.

Among the broader public, FRBs occasionally make headlines whenever speculation arises once again about whether they could originate from extraterrestrial civilizations. This hypothesis is considered highly unlikely among experts and has been dismissed by most researchers. Nevertheless, it keeps finding its way into media reports, which is why it is important to know the difference between a scientific hypothesis and speculation. The current state of research clearly points to natural causes — with magnetars at the top of the list. At the same time, the final answer has not yet been found, which makes FRBs one of the most exciting open problems in modern astronomy.