The universe, despite appearing to be a peaceful place, hides in the depths of the cosmos formidable bursts of energy that cannot be captured by the human eye and that release as much energy as the Sun will produce in its entire useful life. They are the so-called gamma-ray bursts, the most powerful events in the universe that, within a few milliseconds or several minutes, release colossal amounts of energy in distant galaxies. The fact that they are so ephemeral makes them difficult for scientists to observe.
Now, an international team of astronomers led by the University of Maryland (USA) has managed to capture one of these formidable explosions in great detail. Experts have used a wide range of ground and space telescopes to not miss a millisecond of the event, dubbed GRB160625B.
This explosion has revealed key details about the initial “immediate” phase of gamma-ray bursts and the evolution of the large jets of matter and energy that form as a result of the explosion. The findings have been published in the journal Nature.
“Gamma ray bursts are catastrophic events, related to the explosion of massive stars 50 times the size of our Sun. If we classify all the explosions in the universe based on their power, the gamma ray bursts would be right behind the Big Bang.” , says Eleonora Troja, leader of the work.
The data collected from the great explosion suggest that when very massive stars die, collapse in on themselves and give rise to a black hole, this produces a strong magnetic field that initially dominates the jets of energy emission. But, when the magnetic field breaks, matter takes over and dominates those jets of energy; that is, the current results show that both factors play a key role in the emission of gamma ray jets.
“There has been a dichotomy in the scientific community and we found evidence for both models, suggesting that the gamma ray jets have a dual and hybrid nature. The jets start out magnetic, but as they grow, the magnetic field degrades and loses. dominance, matter takes control and dominates the jets, although sometimes a weaker vestige of the magnetic field can survive, “explains Troja.
In addition, the data also allude to the fact that the phenomenon that explains the behavior of these violent outbursts step by step is synchrotron radiation – the electromagnetic radiation generated when electrons move along a curved path at high speed in a magnetic field. Thus, synchrotron radiation would activate the extremely bright initial phase of the burst, known as the “fast” phase.
“ Synchrotron radiation is the only emission mechanism that can create the same degree of polarization and the same spectrum that we observed at the beginning of the explosion. Our study provides compelling evidence that the gamma ray emission caused by synchrotron radiation is an achievement. important because, despite decades of research, the physical mechanism that drives gamma-ray bursts had not yet been unequivocally identified, “says Troja.
The phenomenon is so fast and transient that it requires an almost real-time response to capture it : “Events are unpredictable and once the blast occurs, it disappears. We are fortunate to have observations from a wide variety of sources, especially during the initial, which is very difficult to capture “, says Alexander Kutyrev, co-author of the work.
“This burst was unique because we captured the state of polarization at an early stage. This is difficult to do because it requires a very fast reaction time and there are relatively few telescopes with this ability,” concludes Kutyrev.
Referencia: Significant and variable linear polarization during the prompt optical flash of GRB 160625B. Nature (27 July 2017) doi:10.1038/nature23289
Credit: NASA’s Goddard Space Flight Center / S. Karpov, G. Beskin (SAO RAS and Kazan Federal University, Russia), S. Bondar, E. Ivanov, E. Katkova, N. Orekhova, A. Perkov (OJS RPC PSI , Russia), A.Biryukov (SAI MSU and Kazan Federal University, Russia), V.Sasyuk (Kazan Federal University, Russia)
