How is it a cosmic engine that drives at full blast over days when the strongest explosions ever to take place in the universe tend to fizzle off after a few minutes? It is what astronomers have been grappling with following the discovery of GRB 250702B a gamma-ray burst so long and unusual that it has prompted a reconsideration of the power mechanism of this phenomenon.
1. A Record-Breaking Burst
GRB 250702B was spotted on July 2, 2025, and was visible at least seven hours, which is much longer than the earlier record of the duration of gamma-ray bursts. NASA, Fermi Gamma-ray Space Telescope, Swift Observatory and other spacecraft observations have demonstrated a series of periods during the event of gamma-ray emissions. The afterglow lasted many months, in stark contrast to the short lived nature of most bursts. Brendan O Connor of Carnegie Mellon University explained it as a most fascinating occurrence, which does not fit into any other high-energy transients, which we have ever seen in the last half century.
2. Multi-Wavelength Coordination
To record the whole outburst, no single observatory could be able to do it, and thus the astronomers pieced together data of a collection of instruments. China’s Einstein Probe that detected the X-rays a whole day before the peak of the gamma-rays and NASA Chandra X-ray Observatory and NuSTAR trailed the flares two days later. The thick dust of the host galaxy was cut by the infra-red of the James Webb Space Telescope (JWST), giving a sharply defined dust lane cutting through its core. According to Huei Sears of Rutgers University, the solution to Webb is inconceivable. We can see so vividly that the burst has passed through this dust lane which is pouring across the galaxy.
3. A Galaxy Unlike Typical GRB Hosts
Subsequent spectroscopy put the host galaxy at a distance of approximately 8 billion light-years. It is very huge, it measures more than twice the mass of the Milky Way, and structurally peculiar, perhaps due to a merger. This is in contrast with the small, patchy galaxies which tend to contain long-duration GRBs. This was complicated by the dust-rich environment, as it would have been easy to detect any related supernova, which is usually anticipated in case of a stellar collapse burst.
4. Black Hole vs. Black Hole Scenarios
Two dominant models have come up. One is a black hole with an intermediate mass, a few thousands of solar masses, which has torn apart a star that has strayed too near. The other contains a stellar-mass black hole, just a few times more massive than the Sun, colliding with a stripped helium star and swallowing it up inside. In both of those, matter is drawn into an accretion disk where relativistic jets are emitted which cause the gamma-ray emission. The smaller black hole is consistent with one second scale variability of the Fermi data, which bigger black holes are unable to rapidly fluctuate.
5. Jet Physics and Jet Energy
The jets of the gamma-ray bursts are created when the infalling matter is funnelled by the strong magnetic field into a slim beam travelling at nearly the speed of light. The energy emitted in GRB 250702B was equivalent to 1000 Suns in 10 billion years of Suns. The long period of activity indicates that the central engine, presumably the black hole, accreted material over a much longer duration than possible in normal GRB models. The X-ray examination conducted by O’Connor led to the conclusion that the source of the power of the blast could not be turned off even at the end of the blast.
6. The Morals of Other Foreign Explosions
The X-ray and gamma-ray signatures came on at an odd time reminding other rare multi-stage events, including superkilonovas where a supernova is followed by a merger between neutron stars. Although the origin of GRB 250702B is different, both phenomena indicate the usefulness of multi-messenger astronomy, i.e., the combination of light of different wavelengths with data on gravitational waves, in untangling the complicated astrophysical processes.
7. The use of Advanced Space Telescopes
The sensitivity of the infrared range in JWST enabled the astronomers to identify the structure of the dust in the host galaxy and determine its characteristics even when the host galaxy is very distant. Such instruments, as NIRCam and NIRSpec, offered spectra and images that separated the cases of mergers and dust-lane. These are required to observe transients that are lost in visible light and they are already demonstrating their utility in observing supernovae in the early universe, e.g., GRB 250314A at z 1=7.3, whose SN was as bright and as spectral as local transients like SN 1998bw.
8. GRB Theory has broader implications
A combination of extremely long duration, pre-burst X-rays, and a lack of a distinct supernova makes GRB 250702B difficult to define in terms of short and long bursts (merger of compact objects and collapse of massive stars, respectively). It can be a micro-tidal disruption event by a stellar-mass black hole, a process which hitherto was only associated with supermassive black holes. Everifying this would broaden the existing channels in the manufacture of relativistic jets and gamma-ray emission.
9. The Path Forward
Astronomers are also keeping an eye on the location of the burst in X-rays and radio waves, seeking signatures that might be left behind, to provide some clues about the superiority of competing models. New discoveries of such protracted bursts will be essential in the future. Every time we open a new window of our universe, we realize that we were not comprehending, as Eleonora Troja of the University of Rome told us. GRB 250702B has provided a window on to a world of stellar annihilation and jet-building as never observed before.
