The most powerful explosion in the universe has long been history, but is still being investigated. Now, a research team has made a surprising discovery.
Washington D.C. – When researchers discovered a particularly violent gamma-ray burst in space in the fall of 2022, it quickly got the name "BOAT," the abbreviation for "brightest of all time." In further analysis of the gamma-ray burst GRB 221009A, scientists found that such a huge explosion only occurs about every 10,000 years. "It was probably the brightest burst in X-rays and gamma-rays that has occurred since the beginning of human civilization," Eric Burns of Louisiana State University in Baton Rouge explained at the time.
Astronomers believe that the measured gamma-ray burst was the "birth cry" of a black hole that formed when the core of a massive star collapsed under its own weight. The newly formed black hole quickly absorbs the matter around it and shoots jets of matter (the so-called "jets") into space. These jets travel at almost the speed of light, emitting X-rays and gamma-rays as they make their way through space, which in this case blinded most X-ray and gamma-ray instruments.
Artist's impression of the gigantic gamma-ray burst of October 2022: A black hole launches jets of matter into space that emit X-rays and gamma rays (magenta). © IMAGO/Cover-Images
Massive explosion in space is different from other gamma-ray bursts
Now a research team has apparently found out why the explosion in space was so powerful. The jet that raced through space has a structure never seen before and carried an unusually large amount of stellar material. The research group led by Brendan O'Connor from George Washington University in Washington D.C. took a closer look at the jet and found that it had a narrow core with widely sloping wings. This makes it very different from jets of other gamma-ray bursts, as the research team found and published in a study in the journal Science Advances.
"Our work clearly shows that the gamma-ray burst had a unique structure," explains co-author Hendrik Van Eerten in a statement. Observations have gradually revealed a narrow jet embedded in a wider gas outflow. Normally, however, one would have expected an isolated jet. "For a long time, we thought that jets were shaped like ice cream cones," explains Alexander van der Horst, co-author of the study, in another statement. "However, some gamma-ray bursts in recent years, and in particular the work presented here, show that we need more complex models and detailed computer simulations of gamma-ray bursts."
"The most extreme explosions do not obey standard physics"
The research team already has a theory as to why the structure of the jet is so extraordinary: "Jets from gamma-ray bursts have to pass through the collapsing star in which they form," explains Van Eerten. "We believe that the difference in this case was in the amount of mixing between the stellar material and the jet, so shock-heated gas kept popping up in our line of sight."
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For study leader O'Connor, GRB 221009A represents "a major step forward in our understanding of gamma-ray bursts." It shows "that the most extreme explosions do not obey standard physics." O'Connor goes one step further: "GRB 221009A could be the Rosetta stone that forces us to revise our standard theories." (tab)