Brightest gamma-ray burst came from ‘normal’ supernova

Astrophysicists have used data from NASA’s James Webb Space Telescope (JWST) to determine the source of the brightest gamma-ray burst (GRB) of all time. But their results have opened a new mystery.

Dubbed BOAT (“brightest of all time”), GRB 221009A was observed in October 2022.

Now, it has been shown that the BOAT was generated by the death of a massive star. The star would have initially collapsed in on itself, before violently exploding in a supernova.

The findings are detailed in a paper published in Nature Astronomy.

But it’s not all so straightforward.

“When we confirmed that the GRB was generated by the collapse of a massive star, that gave us the opportunity to test a hypothesis for how some of the heaviest elements in the universe are formed,” says first author Peter Blanchard, from Northwestern University, US.

“We did not see signatures of these heavy elements, suggesting that extremely energetic GRBs like the BOAT do not produce these elements. That doesn’t mean that all GRBs do not produce them, but it’s a key piece of information as we continue to understand where these heavy elements come from. Future observations with JWST will determine if the BOAT’s ‘normal’ cousins produce these elements.”

The BOAT’s light came from approximately 2.4 billion light years away. It flashed across Earth with an intensity at least 10 times greater than any other GRB observed.

“The event produced some of the highest-energy photons ever recorded by satellites designed to detect gamma rays,” Blanchard adds. “This was an event that Earth sees only once every 10,000 years. We are fortunate to live in a time when we have the technology to detect these bursts happening across the universe. It’s so exciting to observe such a rare astronomical phenomenon as the BOAT and work to understand the physics behind this exceptional event.”

The GRB was so bright that astronomers had to wait months for its light to fade to see the supernova that caused it. Blanchard says it was “like the headlights of a car coming straight at you, preventing you from seeing the car itself.”

Initial observations indicated a stock standard supernova.

“It’s not any brighter than previous supernovae,” Blanchard said. “It looks fairly normal in the context of other supernovae associated with less energetic GRBs. You might expect that the same collapsing star producing a very energetic and bright GRB would also produce a very energetic and bright supernova. But it turns out that’s not the case. We have this extremely luminous GRB, but a normal supernova.”

So far, astrophysicists have only been able to confirm the production of heavy elements in the collision of neutron stars. But these mergers take billions of years, which doesn’t account for all the heavy elements like gold and platinum in the universe. That’s why astrophysicists have thought that heavy elements might also be produced by collapsing massive, spinning stars like that which produced the BOAT.

But the lack of heavy elements in the supernova which caused GRB 221009A has left astrophysicists looking for another source.

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