Credit: NOIRLab/NSF/AURA/M. Garlick
The Long Goodbye
Gamma-ray bursts (GRBs) are titanic cosmic explosions discovered by chance in the 1960's by the Vela satellites (designed to detect evidence of titanic nuclear explosions on earth). Largely a mystery at first, our understanding of GRBs has clarified since then, thanks for a crucial breakthrough by the by the BeppoSAX space observatory showing conclusively for the first time that a GRB occurred in a far-away galaxy and was therefore extremely powerful. Studies by the gamma-ray burst monitors on the Compton Gamma-Ray Observatory and the Fermi Gamma-ray Space Telescope and other space observatories showed that these titanic bursts can be divided into "long" bursts, which generally last for a few minutes, and "short" bursts lasting less than a few seconds.
Long bursts are usually believed to signal the supernovae explosion of a very massive star produced at the end of the star's life after it runs out of thermonuclear fuel and collapses. But on July 2, 2025, a gamma-ray burst was discovered by Fermi's Gamma-ray Burst Monitor that lasted not for minutes, but hours.
This burst was named GRB 250702B, and is the longest-lasting GRB ever detected. The burst was also seen by the Burst Alert Telescope on NASA's Neil Gehrels Swift Observatory, the Russian Konus instrument on NASA's Wind mission, the Gamma-Ray and Neutron Spectrometer on NASA's Psyche spacecraft, and Japan's Monitor of All-sky X-ray Image instrument on the International Space Station. X-ray emission from the burst has also been observed by Wide-field X-ray Telescope on China's Einstein Probe, NASA's Chandra X-ray Observatory, and NASA's NuSTAR observatory. Followup observations by Swift, the Hubble Space Telescope, and JWST, and powerful ground-based telescopes, showed that the burst occurred in a distant galaxy about 8 billion light-years from earth, indicating not only that the burst was extremely powerful, but occurred when the Universe was only a fraction of its current age. The extraordinary duration of the burst, its power, and location in both space and time, are a major puzzle. One possibility is that we may have witnessed a black hole in a black hole X-ray binary system leisurely devouring a companion star about 3 times as massive as the Sun, and blasting out a powerful jet of emission in the process, as shown in the artistic illustration above. Other models to explain this record-setting burst have also been proposed.
Published: May 18, 2026
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Page Author: Dr. Michael F. Corcoran
Last modified Tuesday, 26-May-2026 08:18:32 EDT