Found a strange feature in the brightest gamma-ray burst

In October 2022, astronomers witnessed a fleeting, extremely bright gamma-ray burst in the distant Universe. A group of scientists even gave it the name BOAT – “Brightest of All Time”. Now the scientists who recorded it have reported an unusual structure of the jet of this gamma-ray burst.

Artist’s impressions of the gamma-ray burst. Image: NASA

Gamma-ray bursts are one of the biggest fireworks in space. These are huge explosions in space-time that emit gamma rays – the most energetic type of electromagnetic radiation. They mainly occur when massive objects interact, causing large explosions. They can be emitted, for example, by collapsing stars, or their mergers.

The BOAT (officially named GRB 221009A) was about 70 times brighter than any previously recorded gamma-ray burst. It happens in a galaxy that is located at a distance of about 2 billion light-years from Earth. Astronomers believe that such an event occurs only once every 10 thousand years.

An interesting feature of the BOAT

The other day, researchers announced new details of the structure of the gamma ray jet — a huge plume of material ejected from the source of the explosion. It is believed that the explosion and the plume formed from a massive collapsing star that turned into a black hole. Their study was published in the journal Science Advances.

A graphic showing how the jets of a black hole emit gamma rays through the Universe. Graphic material: NASA Goddard Research Center

“For a long time we thought that the jets had the shape of a cone. However, some gamma-ray bursts show that their jets have more complex shapes, so we need to develop more complex models and detailed computer simulations of gamma-ray bursts,” Alexander J. van der Horst, a physicist at George Washington University and co–author of the study, said in a university press release.

Jets of matter almost reaching the speed of light are common for massive objects in the Universe. Quasars and pulsars emit such jets. But the BOAT jets seemed to have a shape that lengthened their radiation, which was noticeable even from terrestrial observatories. Brendan O’Connor, a graduate student at GWU University and the main author of the study, said that the BOAT would change the perception of astrophysicists about the jets emitted by collapsing stars. 

Record-breaking burst

Long-term gamma-ray bursts last more than two seconds. But the glow of the BOAT lasted about 10 hours. According to NASA, long-term bursts are usually associated with the death of stars, while short-term bursts are more likely to occur when stars merge and black holes form.

Although the BOAT was extremely bright, it was not the largest explosion observed in space. Last month, astronomers announced the discovery of a long-term explosion called AT2021lwx. They believe that this explosion occurred as a result of the interaction between the black hole and the surrounding gas.

Future observatories will help researchers to record such bursts at the moment of their appearance, providing astrophysicists with valuable data on even the most fleeting events.

Earlier we reported how a jet of gas in a distant galaxy turned in our direction.

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