(ORDO NEWS) — Astronomers have observed a powerful gamma-ray burst, created not by a newborn black hole, but by a neutron star of unusually large mass.
It held out for a relatively long time before collapsing into a black hole, and scientists have yet to figure out how it did it.
Short gamma-ray bursts are incredibly powerful bursts of energy, the brightest in the modern Universe. They arise when neutron stars merge with each other or with black holes.
It is believed that just in those fractions of a second, during which such a system collapses into a new black hole, it releases as much radiation as the Sun creates in tens of billions of years.
The narrow beam of the gamma-ray burst is visible at vast distances, even by cosmic standards, after which a slowly fading afterglow remains at longer and longer wavelengths.
However, recent observations of the short gamma-ray burst GRB 180618A violate such ideas. Astronomers spotted it using the Swift space observatory in a galaxy more than 10.5 billion light-years away.
Within a couple of minutes after that, the Liverpool robotic optical telescope operating at the Roque de los Muchachos Observatory automatically headed for the object.
Based on the characteristics of the gamma-ray burst, Nuria Jordana-Mitjans (Nuria Jordana-Mitjans) and her colleagues determined that the source of it was not a black hole, but a huge neutron star left after the merger of two smaller neutron stars.
It lasted at least a day before turning into a black hole, as if not immediately “noticing” that it was time to collapse.
“The team was able to find evidence for the existence of a meta-stable, hypermassive neutron star,” said Italian astronomer Stefano Covino, “and this is a very important find.”
According to Nuria Jordan-Mitjans, such stars should not last so long, and why this one lasted so long is not yet known exactly.
Scientists suggest that this may be due to the unusually fast rotation and powerful magnetic fields of the neutron star. For a while, it turned into a millisecond magnetar, which threw out gamma-ray burst streams.
At the same time, the cloud of matter flying around was accelerated by the magnetar to near-light speeds. As it heated up, it created an afterglow that was observed by a ground-based optical telescope.
This radiation turned out to be unusually bright, orders of magnitude larger than usual for such events. However, it did not last long and died out after 35 minutes.
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