Study Sheds Light on Jet Structure of the Brightest Gamma

The brightest ever gamma-ray burst, detected in October last year, may have been powered by its unique jet structure, suggests a new study.

The burst, known as GRB 221009A, is recognised as the largest explosion since the Big Bang. It occurs once every 10,000 years and is 70 times brighter than any previously observed.

However, the reason behind its extraordinary brightness has remained a mystery.

A recent study published in the journal Science Advances utilised NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) observations to investigate how the collapsing star ejected a jet of material with an unprecedented shape among gamma-ray burst jets, along with other distinctive features.

These distinctions may originate from the progenitor star, as its physical properties could influence the burst's characteristics. Alternatively, there could be an entirely different mechanism responsible for launching the brightest jets into space, as suggested by scientists.

Eleonora Troja, Professor of Physics at the University of Rome, who led the NuSTAR observations, explained, "The only way to produce a different jet structure and vary the energy is to vary some property of the star that exploded, like its size, mass, density, or magnetic field. That's because the jet has to basically force its way out of the star. So, for example, the amount of resistance it meets would potentially influence the features of the jet."

Gamma rays, the most energetic form of light in the universe, are invisible to the human eye. However, GRB 221009A, nicknamed BOAT (brightest of all time), was so intense that it overwhelmed most gamma-ray instruments in space. To determine its actual brightness, scientists had to reconstruct the event using data from NASA's Fermi Gamma-ray Space Telescope.

GRB 221009A was also detected by the Hubble and James Webb space telescopes, NASA's Wind and Voyager 1 spacecraft, as well as the European Space Agency's Solar Orbiter.

Like other gamma-ray bursts, GRB 221009A exhibited a jet emanating from the collapsing star, resembling a stream of particles from a fire hose, with gamma rays emitting from the hot gas at its core.

However, unlike previously observed gamma-ray bursts, GRB 221009A displayed a narrow core with wider, sloping sides. While some highly energetic gamma-ray jets have exhibited similar characteristics, the energy of the material in GRB 221009A also varied.

This implies that the energy of the material changed as it moved away from the jet's core, unlike a single bullet shot from a gun. According to the scientists, this phenomenon had not been observed in long gamma-ray burst jets.

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The above article has been published from a wire source with minimal modifications to the headline and text.