Most gamma-ray bursts occur when the core of a star more massive than our Sun collapses, becoming a black hole. However, these are invisible to the human eye. Currently, all recorded gamma-ray bursts have originated in galaxies outside our Milky Way but they were bright enough to be detected billions of light-years away, according to the US space agency Nasa.
A gamma-ray burst (GRB), known as GRB 221009A, was detected on 9 October 2022. It earned the name BOAT, brightest of all time, after it saturated gamma-ray detectors on many space telescopes, according to Space.com. Follow-up studies showed that it was 70 times brighter and significantly more energetic than the previous record holder.
Calling it a once-in-10,000-year event, Eric Burns, an assistant professor of physics and astronomy at Louisiana State University, told Space.com: "So, there's a reasonable chance this is the brightest gamma-ray burst to hit Earth since human civilization began."
Now, scientists who have been studying the BOAT have an explanation for what might have caused it. In a study published June 7, in the journal Science Advances, observations from Nasa’s NuSTAR (Nuclear Spectroscopic Telescope Array) observatory have presented a clue. According to the astronomers, the BOAT had a unique jet structure and was dragging an unusually large amount of stellar material along with it, according to Space.com.
Speaking about the discovery in Nasa’s statement, Brendan O’Connor, lead author of the new study and an astronomer at George Washington University in Washington, said the realisation about the unique jet structure was exciting as “we have no way of studying the star that produced this event; it’s gone now. But we now have some data giving us clues about how it exploded.”
In a previous press statement, O’Connor had said that the BOAT represents a massive step forward in our understanding of GRBs and “demonstrates that the most extreme explosions do not obey the standard physics assumed for garden variety gamma-ray bursts.”
Moreover, the jet of this gamma-ray burst seems to have both wide and narrow "wings" that set it apart from the jets of other GRBs, according to Space.com. This could be why its afterglow continued to be seen by astronomers in multiple wavelengths for months after its initial discovery.
Hendrik Van Eerten, a co-author of the study and scientist at the Department of Physics, University of Bath, said in a press statement published in EurekaAlert: “What we think made the difference, in this case, was the amount of mixing that happened between the stellar material and the jet, such that shock-heated gas kept appearing in our line of sight up to the point that any characteristic jet signature would have been lost in the overall emission from the afterglow."
Van Eerten further added that the findings could help understand other bright GRBs beyond BOAT and help scientists understand the mysteries around such powerful bursts of energy.