Scientists monitor the largest explosion in the universe


A German team has detected a huge explosion more than a billion light-years away from Earth.

Experts revealed the huge explosion of gamma rays, more than a billion light-years away from Earth, to be the largest explosion in the universe captured by astronomers’ camera.

The explosive event marked the death of a star and the beginning of its transformation into a black hole, according to experts from the German Electron Synchrotron in Hamburg.

This was a huge gamma-ray burst, consisting of a mixture of bright gamma-ray flashes and X-rays observed in the sky, emitted from distant extragalactic sources.

It was discovered by the Fermi and Swift space telescopes, supported by the High Energy Stereoscopic System (HESS) telescope on Earth in Namibia.

Despite being a billion light-years away from Earth, this is considered a “cosmic backyard”, coming from the constellation Eridanus.

The German team that monitored it says it is the most energetic radiation and the longest afterglow of gamma rays of any gamma ray burst detected so far.

Previous gamma-ray bursts were an average of 20 billion light-years away.

The explosion, called GRB 190829A, was first detected on August 29, 2019.

The observations from HESS challenge the well-established idea of ​​how gamma rays are produced in these massive starbursts, which come as the birth cries of black holes.

Dr Andrew Taylor of Germany’s Electron Synchrotron (DESY), a co-author on the study, said they were ‘in the first row’ when the gamma-ray burst occurred.

“We can observe the afterglow for several days and to unprecedented energies of gamma rays,” he explained.

The relatively short distance to the gamma-ray burst allowed detailed measurements of the post-aurora spectrum, the distribution of photon energies for radiation in a very high energy range.

Also involved in the research was Edna Ruiz Velasco, a doctoral student at the Max Planck Institute for Nuclear Physics in Germany.

She said they were able to pinpoint its spectrum down to 3.3 TeV, or a trillion times as energy as photons inside visible light.

“This is the very extraordinary thing about a gamma-ray burst – it happened in our cosmic backyard,” Velasco explained. “The high-energy photons were not absorbed in collisions with background light on their way to Earth, as they do at greater distances in the universe.”

The team was able to track the afterglow of GRB 190829A, only the fourth gamma-ray burst detected from Earth, up to three days after the initial explosion.

However, the earlier eruptions occurred much further away, and their subsequent afterglow can only be observed for a few hours each.

These explosions are the largest in the universe, due to the collapse of a rapidly rotating star, said DESY scientist Sylvia Chu, one of the authors of the paper. These stars are in their last moments before turning into a black hole, when a tiny fraction of the liberated gravitational energy fuels the production of a super-small blast wave – detected as a gamma-ray burst.”

“Its rebirth is divided into two distinct phases: an instant, chaotic phase lasting tens of seconds, followed by a long-lasting, smooth fading phase,” she explained.

The team can follow the aurora for up to three days after the initial eruption. The result came as a surprise, as observations revealed strange similarities between X-rays and high-energy gamma-ray emissions from the later aurora.

Well-established theories postulate that the two emission elements must be produced by a separate mechanism, similar to the way particle accelerators on Earth produce bright X-rays for scientific investigations.

However, according to existing theories, it seemed very unlikely that even the most powerful explosions in the universe could accelerate electrons enough to produce directly observed high-energy gamma rays.

This is due to the “combustion limit”, which is determined by the balance of acceleration and cooling of particles inside an accelerator on Earth.

But observations of GRB 190829A’s afterglow now show that both components, X-rays and gamma rays, faded simultaneously. The gamma ray spectrum also clearly coincides with the extrapolation of the X-ray spectrum.

Together, these results are a strong indication that the high-energy X-rays and gamma rays in this afterglow were produced by the same mechanism.


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