DUBLIN, Ireland — Astronomers are facing a profound mystery following the detection of unusual gamma rays that challenge existing understanding of stellar explosions. A recent study published in The Astrophysical Journal Letters describes the phenomenon of gamma-ray burst (GRB) 250702B, which appears to repeat multiple times within a single day. Such bursts typically signify the violent death of massive stars, releasing immense amounts of energy. The study’s authors express astonishment at the implications of this repeated event, raising questions about the possibility of a star re-igniting after a cataclysmic explosion.
Dr. José Martin-Carrillo, an astronomer at University College Dublin and co-author of the study, remarked that this occurrence is unprecedented in over 50 years of observing gamma-ray bursts. GRBs are generally one-time events, resulting from the complete destruction of their stellar source. “This event diverges from everything we know about GRBs, which are catastrophic and should not recur,” he said.
While instances of multiple explosions have been documented in specific binary systems, they do not account for this unique phenomenon. In such cases, a white dwarf siphons energy from a companion star, leading to a sequence of smaller detonations before a final supernova, which typically does not produce several GRBs.
The bursts from GRB 250702B were first detected on July 2 by NASA’s Fermi Gamma-ray Space Telescope, but its unusual characteristics were also observed by the X-ray telescope Einstein Probe a day earlier. Notably, the bursts associated with this event are 100 to 1,000 times longer than most GRBs encountered, further perplexing researchers.
Adding to the intrigue, these gamma rays exhibit a periodic nature—an aspect never before documented in this context. To investigate the origins of this phenomenon, scientists employed the HAWK-I wide-field infrared camera at the Very Large Telescope in Chile, revealing that the gamma rays are emanating from billions of light-years away.
Several hypotheses have emerged regarding the cause of the repeated bursts. One possibility suggests a supermassive star undergoing implosion due to its gravitational collapse, although this would typically result in a brief GRB lasting only seconds. Another scenario proposes that a black hole is consuming a star, but such an event would require highly atypical characteristics of both the star and the black hole involved.
Currently, these theories remain speculative, and researchers acknowledge that it may be some time before the true nature of the event is understood. The discovery of GRB 250702B not only challenges current astrophysical theories but also highlights the complexities and unknowns that continue to exist within the field of cosmic phenomena. As investigations proceed, scientists hope to unlock new insights that could reshape understanding of stellar lifecycles and the origins of gamma-ray bursts.