Scientists pick up a ‘radio heartbeat’ deep inside the cosmos

A radio signal with astonishing periodicity surprised the researchers, who now hope to find others.

Astronomers from MIT and several North American universities have just announced the discovery of a strange and persistent new radio signal from a very distant galaxy that appears to be flashing with astonishing regularity.

The signal is classified as a Fast Radio Burst (or FRB, for Fast Radio Burst). These are very intense radio wave emissions coming from still unknown objects. Usually these signals last for a few seconds before disappearing completely – hence their name.

A fantastic periodic cosmic signal

But this signal called FRB 20191221A is different; it lasts for almost three seconds. It may seem short, but it is an eternity on the scale of an FRB; most of them hold about 1000 times less. And that is not the only peculiarity of FRB 20191221 A. During this three-second window, the researchers also determined that these eruptions of radio waves were emitted in a very specific pattern.

It is repeated every 0.2 seconds – “ a bit like a beating heart “, The authors explain. It will thus be the longest FRB ever documented, and above all it is the first time that one of them presents such an accurate periodicity. ” It is an extreme signal that we have never seen before “say the authors.

The source, on the other hand, is very mysterious. The only certainty for the specialists at the moment is that it is found in a distant galaxy, a few billion light-years from our Earth. But the remarkable peculiarities of the signal could very well help astronomers track the trace.

There are not many things in the universe that emit strictly periodic signals. », Explains Daniele Michilli, postdoc in Astrophysics and Space Research at MIT. Based on what we know about our own galaxy, there are even only two possible candidates: radio pulsars and magnetars.

An artist’s impression of a magnetar. © ESO / L. Calçada

Probably a neutron star

These two terms denote more or less the same class of objects, but with a difference in scale. Either way, we’re talking about a neutron star. It is a celestial body that appears when certain stars reach the end of their lives and deplete all their fuel.

They then undergo what is called a gravitational collapse. Since the nuclear reactions are almost stationary, the compressive forces can no longer compensate for the star’s enormous gravitational force. The star then shrinks to make room for another object, such as a white dwarf, or a neutron star in the case of the largest.

The latter are ridiculously small compared to our sun, and measure barely a few kilometers in diameter. On the other hand, a gigantic mass is concentrated in this small space. That’s why they are exceptionally closewhich gives them fascinating properties for astronomers.

Some of these neutron stars emit strong electromagnetic radiation in a certain direction, in addition to spinning at high speed. We are therefore talking about pulsarsince this signal reaches us as a pulse with each rotation of the star.

In rare cases, these neutron stars may also exhibit an unusually strong magnetic field; we are then talking about magnetars, and they are the most magnetic objects ever documented in the universe. There are even neutron stars that are both pulsars and magnetars.

Astronomers have begun to know the signals associated with these objects relatively well; there are several excellent examples of this in our own galaxy. They could therefore confirm that this strange signal is definitely coming from an object of this type.

The hunt for signals continues

But one important difference fascinated them; while that celestial body is located at a very great distance, the signal it emits is a million times more intense than those emitted by our galaxy pulsars!

This does not mean that astronomers are necessarily dealing with a megamagnet of improbable proportions. According to them, it could mean that the signal is crossing “ an extremely turbulent plasma cloud The latter would behave like a kind of lens that would amplify the signal. But these elements remain hypothetical as the exact origin of the signal remains unknown.

Now astronomers hope they will be able to capture these ” Heartbeat “in the future. This would allow them to refine their conclusions about the origin of the signal, but also about neutron stars in general.” Future telescopes promise to detect thousands of FRBs a month, and at that point we may find new periodic signals like this. “, The researchers conclude.

The text of the study is available here.

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