The brightest gamma-ray burst ever detected, codenamed GRB 221009A, has a strange structure that astronomers have never seen before.
On October 9, 2022, high-energy space surveillance satellites detected an extremely bright gamma-ray signal that suddenly erupted from the constellation Sagittarius; lasted hundreds of seconds. The burst was later determined to be the most energetic flare observed by gamma-ray observatories, and is a magnitude brighter than previous record holders.
Astronomers named GRB 221009A BOAT (Brightest of All Time) and have been watching its afterglow ever since.
“It is 70 times brighter than any other gamma-ray burst detected in more than 50 years of observations,” said Brendan O’Connor, an astronomer at the University of Maryland. The registry. O’Connor is the first author of the study published in academic achievement and was at the time a doctoral candidate at George Washington University,
O’Connor and his colleagues found that the jets emitted by the event – they calculated that the chance for humans to observe such an event would only happen once in 1,000 years – had a strange shape with no clear edge, unlike other gamma rays. GRB 221009A is described as having a narrow core with wide, sloping wings, while other such bursts are shaped more like ice cream cones.
Part of the reason the explosion was so bright is that the rays were aimed directly at Earth, according to Hendrik Van Eerten, co-author of the paper and a researcher at the University of Bath. Van Eerten described this as “much like a garden hose angled to spray right at you.” But this alone is not enough to explain why it is so bright, and its properties do not seem to match observations for most predictive models.
“The combination of extreme gamma-ray brightness and infinite afterglow is fatal for most models because it creates an energy crisis,” Eleonora Troya, lead author of the paper and associate professor at the University of Rome, explained to us. “Using standard theories, we ran into a serious problem: this outburst was a hundred times more powerful than we could explain.”
The energy and structure of GRB 221009A emanates from the star that produced it, leaving behind a black hole estimated to be 30 times the mass of the Sun. “The only way to produce a different jet structure and change the energy is to change some property of the star that exploded, such as its size, mass, density or magnetic field. That’s because the jet has to basically work its way out of the star, so for example the amount of drag it encounters would potentially affect the characteristics of the jet,” O’Connor said.
It is possible that the explosion mixed with the star’s material and produced waves of shock-heated gas that astronomers still detect in the afterglow. They hope to continue studying GRB 221009A and believe it will be observable for several more years. As it begins to fade, the team will watch for any changes and possible interactions with objects in the environment to learn more about the galaxy and star from which it was born.
“Gamma-ray bursts trace the death of massive stars and can allow us to trace the star formation history of the Universe and also specifically the star formation in the galaxies in which they form. They are explosive phenomena showing the most extreme states of matter and magnetic fields, allowing us to observe physical processes that are not reproducible on Earth,” concluded O’Connor. ®