Astronomers are currently scratching their heads after detecting a bizarre, long-lasting cosmic explosion that is unlike anything previously observed. This phenomenon, classified as a gamma-ray burst (GRB), represents a series of repeated outbursts of high-energy radiation. Typically, gamma-ray bursts are the most powerful known explosions in the universe, lasting only from milliseconds to minutes. However, this particular event, officially named GRB 250702BDE, was observed erupting for nearly an entire day in July, baffling scientists worldwide.
According to a study published on August 29 in The Astrophysical Journal Letters, the unprecedented duration of this event has left researchers puzzled. GRBs are generally caused by the death of a giant star, but they are expected to be singular occurrences; their explosive nature means that the source typically does not survive. Antonio Martin-Carrillo, co-lead author and astrophysicist at University College Dublin, stated, “This one is unlike any other in 50 years of gamma-ray burst observations. This event baffled us not only because it showed repeated powerful activity but also because it seemed to be periodic, which has never been seen before.”
The initial detection of GRB 250702BDE was made by NASA's Fermi Gamma-ray Space Telescope on July 2. However, researchers later discovered that the Einstein Probe, an X-ray space telescope operated by the Chinese Academy of Sciences in partnership with European teams, had detected activity from the same event a day earlier, on July 1. To delve deeper into the characteristics of this unusual explosion, a team at the European Southern Observatory (ESO) utilized the Very Large Telescope in Chile's Atacama Desert. While originally believed to have occurred within our galaxy, observations from the Very Large Telescope indicated that the signal originated from beyond it, a finding that was later confirmed by the Hubble Space Telescope.
The study authors explored several possible explanations for this unprecedented repeated explosion. One theory posited that if a massive star—approximately 40 times the mass of the Sun—had died, it would have had to undergo a special type of death where some material continued to fuel the central engine. Another intriguing possibility is that the radiation bursts were generated when a star, possibly a white dwarf, was torn apart by a black hole in what is known as a tidal disruption event (TDE). For this scenario to produce the sustained explosion observed, the black hole involved would need to be an exceptionally rare type, likely an intermediate mass black hole.
Intermediate-mass black holes are intriguing cosmic entities that are larger than stellar-mass black holes—those formed when massive stars collapse—but smaller than the supermassive black holes that reside at the centers of most galaxies. Astronomers theorize that stellar-mass black holes can collide and merge over time to form these intermediate-mass counterparts, yet locating them has proven to be incredibly challenging.
The research team is closely monitoring the aftermath of the explosion and aims to decipher its cause. The next step involves determining the precise location of the explosion, which will enable researchers to measure the energy it generated. Martin-Carrillo expressed optimism, stating, “We are still not sure what produced this or if we can ever really find out, but with this research, we have made a huge step forward towards understanding this extremely unusual and exciting object.”
As astronomers continue to investigate GRB 250702BDE, the scientific community remains eager to uncover the secrets of this extraordinary cosmic event, which could change our understanding of gamma-ray bursts and the dynamics of the universe.
