A team of scientists from the Massachusetts Institute of Technology (MIT) is one step closer to unraveling the source of mysterious radio signals – fast radio bursts (FRBs) with a power of hundreds of millions of suns lasting a few milliseconds. This is close to the limit of energy power that the physics of our Universe is capable of. For the first time, researchers have traced a radio signal to a likely source – a magnetar, 200 million light years away.
Artist’s representation of a fast radio burst from a magnetar. Image source: Daniel Liévano, MIT News
Magnetars are considered the most likely sources of FRBs. However, catching them is not easy. Firstly, these are neutron stars – actually coals from former stars. These cannot be seen through a telescope, especially if they are millions and billions of light years from Earth. Secondly, fast radio bursts do not repeat, so it is impossible to track and predict their source in advance. Scientists can only analyze the recorded signal. And something in this signal gives a clue where to look for its mysterious source.
The recording of a radio signal contains information about its polarization. When radio signals and other radiation travel through space, they ionize gas and dust atoms along the way. This causes the radiation to flicker, which is called scintillation. Also, the radiation acquires one or another polarization, from the characteristics of which one can draw a conclusion about the origin of the signal.
The researchers took into account the fast radio burst FRB 20221022A, discovered in 2022. They were able to trace it to a source 200 million light years away. Analysis of the polarization and “flicker” of the signal made it possible to narrow the region of its origin to a space of 10,000 km across. This is like measuring the width of a DNA helix (2 nm) from the Earth to the surface of the Moon. Finding a needle in a haystack will seem like an easy task compared to this.
The polarization of FRB 20221022A revealed signs of the emission of a signal from a rotating source, which, according to its combined characteristics, can only be a magnetar – a neutron star with the most powerful magnetic fields in the Universe. Researchers believe that this is the most accurate evidence to date of the origin of fast radio bursts, but the question is definitely not completely closed and will require many new observations.