Gamma-ray bursts (GRBs) are timeless explosions in the universe. They release as much energy in just a few seconds as our Sun will over its entire 10 billion-year life. Typically, a GRB occurs when a star goes out with a bang in a supernova, collapsing dramatically and obliterating itself in the process.
What’s got scientists buzzing right now? They’ve come across a GRB that seems to go against all odds. This event didn’t just happen once; it repeated multiple times in just one day—almost like the star endured multiple explosive exits.
Antonio Martin-Carrillo, a researcher from University College Dublin and one of the authors of a new study, stated, “This event is unlike any other seen in 50 years of GRB observations.” His remarks come with their research outlined in The Astrophysical Journal Letters and picked up by news outlets.
According to Martin-Carrillo, “GRBs are catastrophic events expected to fire off just once because the objects that create them don’t survive the furious blast,” adding to the intrigue surrounding this particular signal.
This cosmic signal is already dismissed as just another GRB; it’s known to be far from any previous models of stellar explosions. How can a star pull off something that should outright destroy it multiple times over?
Let’s break down how stars typically meet their end: A massive star, especially one at least several times the Sun’s size, will collapse under its gravitational weight when it runs out of fuel, resulting in a supernova—an explosion scattered across the cosmos.
However, supernovae aren’t all the same. In binary systems where a super-dense white dwarf star strips material from its partner star, occasional thermonuclear fun ensues. A large build-up yields an epic burst, but this still wouldn’t give rise to multiple GRBs in a row.
So, what’s so special about the latest GRB, d GRB 250702B? Detected initially on July 2 by NASA’s Fermi Gamma-ray Space Telescope, it lit up with three distinct bursts. What’s wild is that another telescope, the Einstein Probe, had caught signs of this cosmic crime nearly a whole day prior!
Co-lead researcher Andrew Levan remarked, “This is 100 to 1000 times longer than most GRBs,” highlighting its unusual duration. Furthermore, this event seemed to occur at regular intervals—another property unprecedented for GRBs.
The initial investigation led scientists to believe the signal originated in the Milky Way due to its proximity to the galactic plane. But a follow-up using the HAWK-I camera on Chile’s Very Large Telescope revealed it was actually coming from billions of light-years away!
This next revelation left the team exhilarated. “The fact that this object is extragalactic means that it is potentially much more powerful,” said Martin-Carrillo.
Though several theories are floating around, none have hit the mark yet. One theory suggests that it could be a gigantic star crumbling under its own weight and somehow self-sustaining its flame. Yet, such a scenario might dictate a burst lasting mere seconds.
Another idea is that this might be the result of a tidally disrupted star being engulfed by a black hole. But to meet the characteristics identified, the encounter would involve a highly unusual star and an equally strange black hole.
As for what kind of black hole, there’s speculation that an intermediate-mass black hole might be at play, residing between our typical stellar black holes and the supermassive ones that dominate galaxies. This form of black hole hasn’t yet been directly witnessed, creating what astronomers refer to as a mass gap.
Whether it’s one theory or the other could shift our understanding of stellar explosions, says Martin-Carrillo. “We haven’t pinned down what produced this scenario, but our research brings us significantly closer to unlocking the mystery.”
Curious about more astronomical discoveries? Check out findings regarding a black hole birthed just after the Big Bang.
