Radiation produced by cosmic monster explosions is the greatest ever seen

21 Nov 2019

Illustration of a gamma-ray burst: DESY/Science Communication Lab

Telescopes on Earth have spotted the strongest gamma-ray bursts ever detected, releasing 100bn times more energy than visible light.

Cosmic monster explosions – referred to as gamma-ray bursts (GRBs) – have been spotted emitting energy levels that far exceed anything previously known. Two international teams have published their findings to Nature and Astronomy and Astrophysics revealing that these sudden, short bursts of gamma radiation released 100bn times as much energy as visible light.

Both teams work with the German national research centre, Deutsches Elektronen-Synchrotron (DESY).

While GRBs are often recorded in space, these are the first to be observed by ground-based telescopes. More specifically, they were spotted by the High Energy Stereoscopic System (HESS) in Namibia and the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) in the Canary Islands, Spain.

Since their discovery in the 1960s, the traces of GRBs – called Cherenkov light – are observed in Earth’s atmosphere as a faint blue glow. However, the GRBs themselves had never been detected on Earth up until this point because their brightness falls sharply with increasing energy.

Furthermore, while satellites have been able to detect them in space, their detectors are too small to be sensitive to the low brightness of GRBs at very high energies. So, it was effectively unknown if the monster explosions also emit gamma rays in the very-high-energy regime.

‘That is remarkable!’

These breakthrough detections occurred between summer 2018 and January 2019. Both observations were first spotted by a NASA telescope that triggered HESS and MAGIC to observe the regions of space in less than a minute.

This rapid discovery was then quickly passed on to the entire observational community, meaning another 20 telescopes could watch events unfold. These follow-up observations confirmed that one of the events – GRB 190114C – occurred 4bn light years away. Meanwhile, GRB 180720B occurred even further away, at 6bn light years.

“Having established that GRBs produce photons of energies hundreds of billion times higher than visible light, we now know that GRBs are able to efficiently accelerate particles within the explosion ejecta,” said Konstancja Satalecka, one of the MAGIC scientists.

“What’s more, it turns out we were missing approximately half of their energy budget until now. Our measurements show that the energy released in very-high-energy gamma rays is comparable to the amount radiated at all lower energies taken together. That is remarkable!”

The scientists expect that when the Cherenkov Telescope Array is expected to start operations in 2022, up to 10 massive GRBs could be detected each year.

Colm Gorey was a senior journalist with Silicon Republic