Astronomers have caught fast radio bursts from an unexpected place – an ancient dead galaxy

Today there is no generally accepted theory about the sources of fast radio bursts – short radio pulses lasting a few milliseconds that come from space. This gives them a touch of mystery, including speculation about messages from other civilizations. The new discovery has added even more confusion to the search for the sources of this signal. Discovered in February 2024, the FRB 20240209A signal came from an unexpected place where there should not have been conditions for its appearance.

Image source: AI generation Kandinsky 3.1/3DNews

One of the most popular hypotheses about the origin of these signals suggests that fast radio bursts – short and incredibly powerful radio frequency pulses with the energy of several days of solar radiation in each – are born as magnetars switch electromagnetic field lines. Magnetars are the remains of stars after supernova explosions. After the star sheds its shell, the core remains, which during the compression process becomes a neutron star. Under certain conditions, a neutron star can have a powerful electromagnetic field, which generates impulses in the process of further evolution of the remains.

As the neutron star is aging, the rotation slows down, the energy of which goes to emissions, including fast radio, and, thereby, it loses the magnetic field and the ability to generate them. It is easy to figure out that this is placed by a source of fast radio capes in the active zones of galaxies, where the birth and death of stars is a frequent phenomenon. But with FRB 20240209A, everything turned out to be completely wrong. Since the signal was repeated 21 times, it was possible to detect six times with the help of the second weaker radio telescope (the Chime radio telescope in Canada was the main tool). This gave an exact direction to the signal source.

The location of the source of the radio burst is outlined in an oval, and on the right is the galaxy where everything happened. Image source: Gemini Observatory

The signal from FRB 20240209A was traced to a galaxy that was about 11 billion years old. It was an ancient galaxy with no signs of star formation. Moreover, the signal came from its outskirts, where star formation is, by definition, relatively weak. The probability of finding young magnetars in such a place and under such conditions is very low. They are generated by fairly large stars, and such stars do not live long on a universal scale. Therefore, there may be other, still unknown to us, mechanisms for the occurrence of fast radio bursts.

There is another option that could explain the source of the radio burst from an unusual location. There may be a dense globular star cluster in that distant galaxy. Such clusters are common, and this should not be surprising. Magnetars can merge in them, which can also cause a fast radio burst when the powerful magnetic field lines of these objects intersect. Unfortunately, we do not have the opportunity to find out the details from such a distance. All that remains is to continue observations and hope to register a signal from a more convenient source for observation.