Record-Breaking Gamma-Ray Burst Lasts Seven Hours, Challenging Astronomers Understanding of Cosmic Explosions
Among the universe's most powerful phenomena are gamma-ray bursts—cosmic explosions capable of releasing, in a split second, more energy than the Sun will emit over its entire ten-billion-year existence. Normally, these intense flashes disappear almost immediately, lasting seconds or at most, a few minutes. However, on 2 July 2025, astronomers detected an event that defied every expectation. Instead of ending quickly, the signal persisted for seven hours, produced three distinct bursts throughout a single day and left behind a glowing aftereffect that continued for months. The moment it was observed, scientists recognized that this was no ordinary gamma-ray burst.
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GRB 250702B—The Longest Gamma-Ray Burst Ever Observed
The phenomenon, designated GRB 250702B, was captured by Fermi Gamma-ray Space Telescope and has since been identified as the longest gamma-ray burst ever documented. Its duration eclipses all previously known bursts.
Since 1973, when gamma-ray bursts were first recognized, around 15,000 such events have been recorded, yet only a handful approach the extraordinary length of this one.
Under normal circumstances, gamma-ray bursts are singular occurrences triggered by catastrophic cosmic events, such as:
- The merger of neutron stars
- The collapse of a massive star
GRB 250702B does not appear to match either scenario.
As one scientist from the detection team explained:
"This is certainly an outburst unlike any other we've seen in the past 50 years."
Since then, astronomers have been working relentlessly to understand its true origin.
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Could an Intermediate-Mass Black Hole Be Responsible?
A new study published in Monthly Notices of the Royal Astronomical Society examines a particularly intriguing explanation for the extraordinary event: the presence of an intermediate-mass black hole.
Black holes vary enormously in size:
- Stellar-mass black holes form when massive stars collapse and usually weigh several times the mass of the Sun.
- Supermassive black holes reside at the centers of galaxies and can reach millions or even billions of solar masses.
- Intermediate-mass black holes fall between these extremes, with estimated masses ranging from hundreds to one hundred thousand times the mass of the Sun.
Despite strong theoretical predictions of their existence, locating these mysterious black holes has proven surprisingly difficult.
A Star Torn Apart by Extreme Gravity
The scientists behind the study suggest that GRB 250702B may have originated when a star comparable to our Sun ventured too close to one of these hidden black holes.
The intense tidal forces would have:
- Torn the star apart
- Stretched it into long streams of gas
- Gradually fed the material into the black hole
As the stellar debris spiraled toward the black hole and was slowly consumed, enormous energy was released. This process likely generated a powerful relativistic jet of particles moving at nearly the speed of light, producing the remarkable gamma-ray emission detected by the Fermi telescope.
Repeating Bursts Suggest a Gradual Destruction
Significantly, the repeating pattern of the burst aligns closely with this interpretation.
The star may not have been destroyed instantly. Instead, theoretical models indicate that it could have been gradually stripped apart during several close encounters with the black hole before its final destruction.
Each encounter ma have:
- Torn away additional stellar material
- Triggered a new surge of energy
- Produced another gamma-ray burst
This could explain the nearly regular spacing between the three bursts recorded by Fermi.
Event Located Far From the Galaxy's Center
The location of the event offers another compelling clue.
GRB 250702B lies roughly 5.7 kiloparsecs from the center of its host galaxy, far from the region where the galaxy's supermassive black hole resides.
Astronomers note that such a position is exactly where a roaming intermediate-mass black hole might be found.
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If this interpretation proves accurate, GRB 250702B could mark the first direct observation of a relativistic jet produced by an intermediate-mass black hole consuming a star.
Such a discovery would place the event among the most significant astronomical observations of the decade.
However, the mystery is far from solved.
Several competing explanations remain under investigation and scientists continue to debate the available evidence.
In astronomy, many of the most important discoveries begin with unexpected observations—and a seven-hour cosmic explosion is precisely the kind of puzzle that pushes the boundaries of scientific knowledge.
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