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8th of May 2023
The brightest gamma-ray burst ever detected
The brightest gamma-ray burst (GRB) ever seen, GRB 221009A, was first reported when NASA’s Neil Gehrels Swift Observatory detected X-rays on 9 October 2022. Calculations show that for the few seconds it lasted, the blast deposited around a gigawatt of power into Earth’s upper atmosphere -- equivalent to terrestrial power station’s energy output! Follow-up observations pinpointed the burst to a distant galaxy that lies behind the Milky Way. ASKAP was one of the many telescopes that observed the afterglow of the GRB in the days and weeks that followed.

One of the spectacular results came from ESA's XMM-Newton satellite which revealed the way the X-rays from the GRB have illuminated dust clouds in our galaxy. The radiation travelled through intergaalactic space for around two billion years before entering our galaxy. It then encountered the first dust cloud around 60,000 years ago, and the last one about 1000 years ago. Each time the X-rays encountered a dust cloud, it scattered some of the radiation, creating concentric rings that appeared to expand outwards, as shown in the image above. XMM-Newton observed these rings for several days after the GRB. The closest clouds produced the largest rings simply because they appear bigger by perspective.

However, the GRB has thrown up a mystery as well: it was expected the GRB would have been produced in a supernova explosion which would have become visible at optical wavelengths, but the James Webb and Hubble space telescopes have been used to look for the aftermath of the explosion -- and to date have found nothing. Further observations, and continued monitoring of the afterglow, are planned.

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