Dead galaxy mystery: Fast radio burst confused astronomers

Astronomers have detected for the first time a fast radio burst whose source is located in the vicinity of an old elliptical galaxy that no longer forms new stars. Previously, such phenomena have been associated with much younger galaxies.

Fast radio burst in an artist’s impression. Source: Jingchuan Yu, Beijing Planetarium

Fast radio bursts (FRB) are powerful radio pulses with a duration of a few milliseconds. Their typical energy is equivalent to the energy radiated by the Sun in a few days. The prevailing theory is that the sources of FRBs are magnetars — neutron stars with exceptionally strong magnetic fields. Such objects are formed by the collapse of young and massive stars. Therefore, until recently, astronomers usually associated FRBs with regions of active star formation.

But a discovery made last year is likely to make scientists reconsider. In February 2024, a new source of fast radio bursts was recorded. It was designated FRB 20240209A. In total, FRB 2024020209A produced 22 pulses between February and July 2024.

Astronomers have managed to establish the location of FRB 20240209A. It turned out that the source of the bursts was in a galaxy located 2 billion light-years from Earth. Its mass is 100 billion times that of the Sun, making it one of the most massive galaxies producing radio bursts.

The parent galaxy of source FRB 20240209A (yellow object in the lower right corner, indicated by blue lines) and its suspected location (highlighted by ellipses). Source: Vishwangi Shah et al, 2025

What is most unusual is that we are talking about a “dead” elliptical galaxy. It is 11.4 billion years old, populated exclusively by old stars, and shows no evidence of young luminaries or signs of star formation. At the same time, while most FRBs originate in the central regions of galaxies, FRB 20240209A is at the very outskirts of its home — 130,000 light-years from the center, where in principle there are not so many stars.

According to the researchers, a possible explanation for this mystery is that FRB 20240209A is located in a globular cluster, a dense group of stars held together by gravitational forces. Such structures are promising sites for magnetars, possibly formed by mechanisms other than giant star collapses — for example, neutron stars merging or as a result of a white dwarf collapsing under its own gravity. In any case, the discovery supports the suggestion that FBRs may have more sources of origin than previously thought.

According to news.northwestern.edu

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