Astronomers have detected a repeating radio signal, captured multiple times, originating from an ancient and inactive galaxy. This discovery challenges current theories about the origin of fast radio bursts, opening new perspectives on the evolution of neutron stars.
Fast radio bursts (FRBs) are intense bursts of energy, released in a few milliseconds. Although their origin often remains mysterious, they are generally associated with young and magnetized neutron stars. However, the recent detection of a repeating FRB in a galaxy over 11 billion years old overturns this idea.
Fast radio bursts: a cosmic enigma
FRBs are extremely energetic astrophysical phenomena, capable of releasing in an instant the equivalent of the energy emitted by the Sun in a day. Until now, they were mainly attributed to magnetars, neutron stars with intense magnetic fields. However, their exact mechanism remains poorly understood.
The repetition of some FRBs, like the one observed in 2024, suggests that their source is not destroyed during the emission. This rules out the hypothesis of unique cataclysmic events, such as supernovas, and directs research towards more long-lasting processes.
An ancient galaxy full of surprises
FRB 20240209A was located at the edge of a galaxy situated two billion light-years away. This galaxy, over 11 billion years old, has not formed stars for a long time. Yet, it harbors a source of repeating radio bursts, contradicting the idea that only young magnetars can produce such signals.
This discovery raises questions about the longevity and activity of neutron stars. Researchers consider that unusual mechanisms, such as the merging of ancient magnetars, could explain these energetic emissions.
Revisited hypotheses
One of the avenues explored is that the FRB originates from a globular cluster orbiting the galaxy. These clusters, rich in ancient stars, could host younger magnetars resulting from stellar mergers. Another possibility is that aged neutron stars, long considered inactive, could still release radio bursts.
These scenarios, although speculative, show that FRBs could have more varied origins than expected. They encourage scientists to revise their models and explore new astrophysical mechanisms.
Implications for future research
This discovery paves the way for new studies to understand the diversity of FRB sources. Multi-wavelength observations and numerical simulations will be essential to test the proposed hypotheses. Moreover, more powerful telescopes, like the James Webb, could allow for the precise identification of the involved globular clusters.
By revealing that ancient galaxies can still harbor energetic phenomena, this study broadens our understanding of stellar and galactic evolution. It reminds us that the Universe retains many secrets waiting to be discovered.
To go further: What is a globular cluster?
A globular cluster is a dense grouping of hundreds of thousands to several million stars, held together by gravity. These clusters are among the oldest structures in the Universe, with ages often exceeding 10 billion years. They orbit around galaxies, mainly in their halo.
The stars in a globular cluster are mostly ancient and poor in heavy elements. Unlike young open clusters, they no longer form stars. Their high stellar concentration favors intense gravitational interactions, which can lead to the formation of compact objects like neutron stars or magnetars.
Some globular clusters contain millisecond pulsars, rapidly rotating neutron stars accreting matter from a stellar companion. This peculiarity makes them natural laboratories for the study of stellar evolution and the effects of extreme gravity.
The study of globular clusters also helps to understand galaxy formation. Their population and distribution provide clues about the early phases of the Universe, revealing details about galaxy dynamics and their cosmic past.
Article author: Cédric DEPOND