The brightest explosions in the universe, the GRBs or bursts of gamma rays, are possibly stronger and more durable than previously thought, an unexpected finding that calls into question everything that was known about these cosmic events.
This is the conclusion reached by an international team of researchers from the HESS collaboration – made up of 41 institutes from 15 countries around the world – after observing and studying a GRB that has generated the most energetic radiation and longest glow ever captured.
Furthermore, studying the data suggests that the X-rays and gamma rays from these huge stellar explosions have the same cause and are not, as previously believed, caused by separate processes. The details of this study were published in the journal Science.
GRBs are the most violent explosions in the universe since Big Bang, in a few seconds they release an energy comparable to that which the Sun would emit throughout its life and suddenly appear in the sky, at a rate of approximately one a day.
This phenomenon was discovered in the late 1960s by American satellites during the Cold War and is believed to arise from the collapse of massive stars or the merger of neutron stars in distant galaxies.
These bursts have two emission phases, the prompt, which lasts between a few seconds and one or two minutes, and the afterglow, which leaves a prolonged glow that slowly fades and that, until now, had only been observed at low energies, he explains. to EFE the physicist from the Institute of High Energy Physics of the Autonomous University of Barcelona Òscar Blanch.
But, after 15 years of effort investigating the behavior of GRBs, the MAGIC collaboration telescopes detected for the first time “A GRB at the highest energies”. It was January 14, 2019 and Blanch was part of that team.
This phenomenon emitted 50% more energy than that registered in other bursts and, thanks to the fact that it arose from a nearby galaxy (about 4.5 billion light years from Earth), it could be followed well.
Now, thanks to special telescopes at the HESS observatory in Namibia, an international team has reported the most energetic radiation of a gamma flash ever recorded, followed by the longest glow.
The explosion, detected on August 29, 2019 by NASA satellites “Fermi” and “Swift” and christened GRB 190829A, arose from the southern constellation of Eridanus, about a billion light years from the Land, making it one of the closest explosions observed to date (the typical burst is usually about 20 billion light years away).
“We were really sitting in the front row when the gamma-ray burst happened. We recorded the glow as soon as it entered the HESS telescope’s field of view and we were able to observe the afterglow for several days at unprecedented energies, ”recalls Andrew Taylor, a DESY researcher and co-author of the study.
The close range of the blast allowed the researchers to make detailed measurements of the high-energy spectrum of its glow, that is, the “color” or energy distribution of X-ray and gamma-ray photons (light particles).
“We were able to measure the spectrum of GRB 190829A down to an energy of 3.3 tera electron volts (TeV), which is around a trillion times more energetic than visible light,” the co-author details. Edna Ruiz-Velasco, from the Max Planck Institute for Nuclear Physics in Heidelberg.
The observations of the blast challenge established theories because they revealed “a striking similarity between the X-ray component and the very high-energy gamma radiation in the afterglow,” explains Sylvia Zhu, a researcher at DESY.
And it is surprising, because according to the most accepted theory, X-rays and gamma radiation have to be produced by different mechanisms but this study has shown that in GRB 190829A, both components faded synchronously, indicating that they were produced by the same mechanism.
But to change the current theory of outbursts of gamma rays more observations will be needed. Next-generation instruments, such as the Cherenkov Telescope Array, which is being built in Chile and on the Canary Island of La Palma, will surely help to record these outbursts more regularly.