A mysterious repeated signal reaches us from a distant galaxy

A mysterious repeated signal reaches us from a distant galaxy

If you are not passionate astronomy or astrophysics, it is unlikely that you have ever heard of fast radio bursts or FRB (for fast radio bursts). These mysterious phenomena, however, deserve special attention: they are kinds of flashes, more precisely bursts of radio waves lasting a few milliseconds, very intense and above all, emitted by unidentified sources in the cosmos.

First discovered in 2007 by astronomer Duncan Lorimer, they have been spotted dozens of times by radio telescopes around the world.

According to the scientific magazine ScienceAlerta new study might have identified the nature of an FRB source.

This source, first detected in 2019 and named “FRB 190520B,” regularly spits out bursts of fast radio bursts. Astronomers have been able to analyze information about their provenance in the universe that suggests there are several different mechanisms capable of producing these strange waves.

A long time ago, in a galaxy far, far away…

Most of the time, FRBs come from other galaxies (only one source has been spotted in ours, the Milky Way) and they are extremely bright, releasing as much energy in an instant as 500 million suns.

Also, they are usually only detected once, which makes them as difficult to trace and study as they are impossible to predict. Only three sources were spotted more than once.

The signals detected in the Milky Way came from a dead star called “magnetar”indicating that at least some FRBs are caused by magnetar flares.

Kshitij Aggarwal, astrophysicist at West Virginia Universityasked the following question: “Are signals that repeat themselves different from signals that are detected only once?”

Since the signal from FRB 190520B repeats itself, observations could be made by the radio telescope Karl G. Jansky Very Large Array. They reveal intriguing features: the source is located on the outskirts of a very old dwarf galaxy, nearly 4 billion light-years away. Moreover, between the strong signals, much weaker signals were detected, suggesting that the FRBs come from a compact and persistent radio source.

If you are a fan of FRBs, these characteristics will be familiar to you: they are the same as those of another repeating signal: FRB 121102. It was the first whose source could be traced to the outskirts of a dwarf galaxy (3 billion light-years away) and it too is associated with a compact and persistent source.

The discovery of FRB 190520B is therefore consistent with a hypothesis of the scientists: there could be at least two mechanisms responsible for FRBs. Thus, the different bursts could be emitted either by various objects, or by the same type of object at various stages of its evolution.

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