The most powerful space explosion ever seen keeps baffling astronomers

GRB221009A surrounded by dust rings

ESA/XMM-Newton/M. Rigoselli (INAF)

The most powerful explosion ever seen may break our understanding of how these cosmic cataclysms, called long gamma ray bursts (GRBs), work. The burst was spotted in October 2022, and it is proving difficult to explain despite continued observations and analyses by researchers around the world.

When the burst, called GRB221009A, was spotted, astronomers dubbed it “the BOAT” – the brightest of all time. Eric Burns at Louisiana State University and his colleagues compared it with other GRBs and found that events this bright probably only occur once every 10,000 years or so, so the nickname fits.

“It’s probably the brightest event to hit Earth since human civilisation began,” says Burns. “The energy of this thing is so extreme that if you took the entire sun and you converted all of it into pure energy, it still wouldn’t match this event – there’s just nothing comparable.”

Other astronomers have continued to monitor the afterglow of the burst in order to determine the mechanism behind it. Most long GRBs are thought to form when the core of a star runs out of fuel and collapses, forming a black hole and stirring up the remaining stellar material into powerful jets.

But when other researchers observed the GRB’s afterglow in radio wavelengths, what they found didn’t quite match that simple model. The energy of the jet evolved smoothly and relatively slowly over time, whereas we expect there to be fast jumps in energy as the jet evolves.

Also, for these kinds of GRBs, it is generally expected that a supernova will occur weeks after the initial burst as the energy from the collapse of the star’s core blasts through its outer layers. But it isn’t clear whether that happened with GRB221009A. “We can’t even agree on whether or not we’ve seen a supernova, and if we haven’t, then we’ve really broken our understanding of these events,” says Burns.

“We have this idea of how it should look a day later and a week later and a month later, and we cannot get any of these things to line up in a self-consistent manner,” says Burns. “When you really dig into it, all of our models are failing.” Astronomers are continuing to monitor the GRB’s afterglow and work to understand it, but so far the BOAT is so strange that we might have to build a new model of how GRBs work more generally.


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