Scientists record best view yet of ‘gargantuan’ cosmic explosion

4 Jun 2021

Artist’s impression of a relativistic jet of a gamma-ray burst breaking out of a collapsing star and emitting very-high-energy photons. Image: DESY Science Communication Lab

Researchers in Ireland were part of an international team that dissected the afterglow of a gamma-ray burst in ‘our cosmic backyard’.

Scientists have gained the best view ever recorded of a gamma-ray burst – the brightest explosion in the universe.

An international team, including researchers from the Dublin Institute for Advanced Studies (DIAS), recorded this event at a specialised observatory in Namibia.

It was one of the closest gamma-ray bursts to Earth ever observed, at a distance of roughly 1bn light years away. A typical gamma-ray burst is around 40bn light years away.

This relatively short distance allowed researchers to take detailed measurements of the afterglow of the gamma-ray burst. This spectrum of colours represents the photon energies of the radiation, which were in the very-high energy range.

It emitted photons at an energy level of up to 3.3 teraelectronvolts – which is about a trillion times as energetic as the photons of visible light and marks the highest energy spectrum of a gamma-ray burst recorded to date.

The High Energy Stereoscopic System (HESS) recorded the event, catalogued GRB 190829A, in August 2019.

More than 230 scientists from 41 institutes in 15 countries contributed to the research, which was published this week in Science.

Prof Felix Aharonian, a professor in astronomy and astrophysics at DIAS, was involved in the discovery.

He said that since the gamma-ray burst happened “in our cosmic backyard”, the very-high-energy photons were not absorbed in collisions with background light on their way to Earth, which is what typically happens over larger distances in the universe.

“This enabled us to examine the explosion with an unprecedented level of detail,” he said, adding that the findings could challenge the conventional gamma-ray burst theory.

“We were able to determine that the characteristics of the gamma-ray and x-ray radiation are strikingly similar, so that the simplest explanation is that they were produced together by the same radiation process. This is quite unexpected and poses challenges to the prevailing theories of gamma-ray bursts.”

Dr Jonathan Mackey, a DIAS research fellow also working on the HESS project, added that the implication of this discovery highlights the need for further studies.

“GRB 190829A is only the fourth gamma-ray burst detected from the ground at very high energies,” he said.

“Looking to the future, the prospects for the detection of gamma-ray bursts by next-generation instruments look promising, which will help us to fully understand these gargantuan cosmic explosions.”

Sarah Harford was sub-editor of Silicon Republic