The gamma-ray burst GRB 221009A, recorded at the end of last year, turned out to be the strongest in the last 10 thousand years. This conclusion was reached by a group of scientists led by astrophysicist Eric Burns from Louisiana State University. The results of the study were published in The Astrophysical Journal Letters.
Burns and his colleagues found evidence that this gamma-ray burst surpassed all earlier observations in terms of its energy characteristics. It exceeded them both in terms of peak power and total energy released. Scientists emphasize that the distance from which the burst came to us – 2 billion light years – is quite close to our Galaxy by the standards of such events.
According to Burns and his colleagues, such a surge occurs no more than once every 10,000 years, and a surge with a similar peak power no more than once every 15,000 years. This is the rarest event not only on the scale of human life, but also on the scale of the entire time of the existence of human civilization.
At the end of March this year, a special issue of The Astrophysical Journal Letters dedicated to this event was published . This week, an article about the burst GRB 221009A was published by the journal Physics today.
At the end of last year, astronomers noticed the arrival of gamma rays from the constellation Arrows from a distance of about 2 billion light years. The flare, which received the number GRB 221009A, was recorded by the Fermi Gamma-ray Space Telescope, and later by the Swift space observatory, which automatically instructed terrestrial observers to direct telescopes to see the afterglow from the burst. Then ground-based telescopes recorded the afterglow at the point in the sky where the gamma rays came from.
The study of the GRB 221009A gamma-ray burst is important not only for understanding the mysteries of the Universe as a whole, but also for studying our Galaxy: gamma radiation has revealed several dust clouds within the Milky Way. Astrophysicists have tried to find the neutrinos accompanying the gamma-ray burst, but have failed. Apparently, it will not work to see neutrino fluxes from weaker bursts either.
The gamma-ray burst was supposed to be accompanied by a supernova explosion, but the Hubble and James Webb space telescopes, aimed at the point where the gamma rays came from, did not detect any supernova remnants. Only the afterglow was visible. A possible explanation could be that the formed black hole promptly "ate" all the remnants of the supernova.
Gamma-ray bursts are astronomical events during which a huge amount of energy is released in the form of gamma rays in a short period of time. These are the most powerful events in space since the Big Bang. Gamma-ray bursts do not last long: from hundredths of a second to several hours, and then fade. In place of the source of gamma radiation, an afterglow is observed in longer wavelength ranges – X-ray, optical, microwave and radio. In terms of the power of its radiation, a gamma-ray burst can exceed an entire galaxy. During a gamma-ray burst, as much energy can be emitted in a few seconds as the Sun will emit in 12 billion years of its existence.
The mechanism of occurrence of gamma-ray bursts is not fully understood. It is assumed that short (less than two seconds) gamma-ray bursts occur when two neutron stars collide. Long gamma-ray bursts are thought to be produced when the core of a massive star collapses. In this case, a black hole remains from the core of the star, and the substance adjacent to it flies out from the poles of the star in powerful “jets” (jets); the rest of the star explodes as a supernova.
Gamma-ray bursts are extremely rare. None of them has yet been registered in our Galaxy. There is a hypothesis that, if such a burst occurred within the Milky Way, it would lead to the complete or partial death of all life on Earth due to hard electromagnetic radiation. Those bursts that astronomers record occur far from us, at distances measured in billions of light years.
The first gamma-ray bursts were recorded in the 1960s by American satellites, which were originally designed to search for evidence of atmospheric and ground nuclear tests conducted by the USSR. Since then, about 12,000 gamma-ray bursts have been recorded.