Astronomers have noticed the longest gamma-ray burst ever seen, a cosmic explosion that lasted seven hours — and so they decided it could possibly be the work of a black gap destroying a star.
Gamma-ray bursts (GRBs) are thought-about to be essentially the most highly effective cosmic explosions for the reason that Large Bang, however when GRB 250702B was first detected on July 2, 2025 by NASA’s Fermi Gamma-ray House Telescope, it shortly stood out among the many round 15,000 GRBs detected up to now. The blast could possibly be the results of an elusive intermediate-mass black gap devouring a star.
“The preliminary wave of gamma rays lasted at the least 7 hours, almost twice the length of the longest GRB seen beforehand, and we detected different uncommon properties,” workforce member Eliza Neights of George Washington College and NASA’s Goddard House Flight Heart in Greenbelt, Maryland, mentioned in an announcement. “That is definitely an outburst not like every other we have seen prior to now 50 years.”
Following up on Fermi’s preliminary detection, astronomers turned to the Very Giant Telescope (VLT) situated on Cerro Paranal within the Atacama desert of northern Chile. This revealed the placement from which the GRB erupted, a galaxy billions of light-years away from the Milky Manner.
Investigating the afterglow of GRB 250702B with three of the world’s strongest ground-based telescopes, the Víctor M. Blanco 4-meter Telescope and the dual 8.1-meter Worldwide Gemini Observatory telescopes, a workforce of researchers led by Jonathan Carney, of the College of North Carolina at Chapel Hill, discovered clues as to what precipitated this record-breaking explosion.
“The power to quickly level the Blanco and Gemini telescopes on quick discover is essential to capturing transient occasions resembling gamma-ray bursts,” Carney mentioned in an announcement. “With out this capacity, we might be restricted in our understanding of distant occasions within the dynamic night time sky.”
What precipitated the longest gamma-ray burst ever recorded?
This analysis recommended that the preliminary gamma-ray sign from GRB 250702B emerged from a slim, near-light-speed jet of plasma slamming into surrounding gasoline and dirt. This means that the galaxy that’s residence to this occasion is full of an unlimited quantity of mud across the level of emission. The workforce additionally discovered that the host galaxy of GRB 250702B is extra huge than these of different GRBs.
One present idea in regards to the creation of GRBs suggests they occur when huge blue supergiant stars collapse on the finish of their lives, when an excessive neutron star referred to as a magnetar is born, or when a black gap rips aside a star in a so-called “tidal disruption occasion” (TDE). Nevertheless, GRB 250702B would not appear to utterly fall in step with any of those eventualities.
Researchers at the moment have three concepts of what occasion may have launched this record-breaking GRB. The primary would contain a black gap colliding with a star that has had its outer layers of hydrogen stripped and is now composed principally of helium.
The second state of affairs suggests a star or a smaller stellar physique like a brown dwarf or perhaps a planet may have encountered the immense gravitational affect of a black gap or a neutron star, leading to a smaller, much less highly effective TDE-type occasion referred to as a micro-tidal disruption occasion.
The third potential launch mechanism for GRB 250702B includes an elusive class of black gap referred to as an “intermediate mass black gap,” with a mass starting from 100 instances that of the solar, to 100,000 instances the mass of our star. Even if scientists consider the cosmos is full of these middle-of-the-road black holes, they’re not often detected. If this state of affairs is the appropriate match for GRB 250702B, this could symbolize the primary time astronomers have noticed an intermediate-mass black gap producing a plasma jet after ripping up a star.
“This work presents an interesting cosmic archaeology drawback through which we’re reconstructing the small print of an occasion that occurred billions of light-years away,” Carney mentioned. “The uncovering of those cosmic mysteries demonstrates how a lot we’re nonetheless studying in regards to the universe’s most excessive occasions and reminds us to maintain imagining what could be taking place on the market.”
The workforce’s analysis was revealed in November in The Astrophysical Journal Letters.
