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Researchers discover brightest gamma-ray burst ever observed

Researchers from the University of Alabama in Huntsville (UAH) have made an extraordinary discovery at the Center for Space Plasma and Aeronomic Research (CSPAR). They found a gamma-ray burst (GRB) in the constellation Sagitta, located approximately 2.4 billion light-years away. This GRB stands out as the brightest ever observed and is believed to have originated from the collapse of a massive star, resulting in a supernova explosion and the birth of a black hole.

The team behind this remarkable finding consists of Dr. Peter Veres, an assistant professor at CSPAR, Dr. Michael S. Briggs, CSPAR principal research scientist and assistant director, and Stephen Lesage, a UAH graduate research assistant. Their work revolves around operating the Gamma-ray Burst Monitor (GBM) aboard the Fermi Gamma-ray Space Telescope, which orbits low-Earth and scans the gamma-ray sky for GRBs.

The GBM is an essential instrument developed through collaboration between the National Space Science and Technology Center in the U.S. and the Max Planck Institute for Extraterrestrial Physics in Germany. Managed at NASA's Marshall Space Flight Center in Huntsville, AL, the GBM's primary mission is to hunt for GRBs.

Dr. Veres explained that this particular gamma-ray burst was exceptionally bright, an event that they would expect to encounter only once every 10,000 years. Normally, the team detects around five GRBs per week, but this one overwhelmed the instrument with its high number of incoming photons. Stephen Lesage played a vital role in reconstructing the lost data caused by the burst's brightness.

Gamma-Ray Burst 221009A occurred approximately 2.4 billion light-years away in the direction of the constellation Sagitta. Credit: Courtesy International Gemini Observatory

Gamma-ray bursts (GRBs) are unpredictable cosmic events that emanate from various directions in the sky. To effectively observe these bursts, the Gamma-ray Burst Monitor (GBM) continuously scans as much of the sky as possible. It comprises 12 detectors containing sodium iodide, which captures and low-energy gamma rays, and two detectors made of bismuth germanate, specialized for high-energy gamma rays.

When gamma rays interact with the instrument's crystals, they produce light. By analyzing which crystals emit light, the GBM can determine the direction of the bursts. So far, the Fermi instrument has identified over 3,500 GRBs, with 221009A standing out as the brightest ever detected.

Dr. Veres explains that during a GRB, a massive star, about 30 times more massive than the sun, meets its demise, leading to the formation of a black hole. This black hole generates an ultra-fast jet, nearly approaching the speed of light, resulting in the gamma-ray burst. As time progresses, GRBs become visible across various wavelengths, from radio and optical to high-energy gamma-rays, known as the afterglow of the GRB. Interestingly, this particular GRB was so intense that its afterglow was observable in the Gamma-ray Burst Monitor, a rare occurrence, allowing scientists to study it for nearly three hours.

GRB 221009A also stands out for being one of the closest and possibly most energetic GRBs ever discovered, as documented in a forthcoming publication in The Astrophysical Journal Letters, available on the arXiv preprint server. This groundbreaking finding provides valuable insights into these enigmatic celestial events, pushing the boundaries of our understanding of the universe.

Source: University of Alabama in Huntsville

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