A cosmic explosion of gigantic proportions kept astronomers on tenterhooks in mid-October – the closest and possibly most energetic gamma-ray burst (GRB) ever observed. The GRB, designated GRB 221009A, occurred at a distance of about 2.4 billion light-years in the direction of the constellation Arrow. It was first detected on the morning of Oct. 9 by X-ray and gamma-ray space telescopes, including NASA’s Fermi Gamma-ray Space Telescope, the Neil Gehrels Swift Observatory and the Wind spacecraft.

As news of this discovery quickly spread, two teams of astronomers worked closely with Gemini South staff to obtain the earliest possible observations of the afterglow from this historic explosion. The teams now have access to both data sets for their analyses of this energetic event. “The exceptionally long GRB 221009A is the brightest GRB ever recorded, and its afterglow breaks all records at all wavelengths,” said Brendan O’Connor of the University of Maryland. “Because this outburst is so bright and also so close, we believe this is a unique opportunity to answer some of the most fundamental questions about these explosions, from the formation of black holes to tests of dark matter models.”

Astronomers believe that this is the collapse of a star many times the mass of our Sun, triggering an extremely powerful supernova that is now forming a black hole 2.4 billion light-years from Earth. When black holes form, they propel powerful jets of particles that are accelerated to near the speed of light. These jets then break through the remnants of the progenitor star, emitting X-rays and gamma rays as they stream into space. When these jets are directed toward Earth, they can be observed as bright flashes of X-rays and gamma rays.

Because of its relative proximity to Earth, this event also provides a unique opportunity to better understand the origin of heavier-than-iron elements and whether they all originate only from neutron star mergers or also from collapsing stars that trigger GRBs.