Astronomers have discovered a remarkable cosmic event: a gamma-ray burst (GRB) named GRB 250702B. This explosion of high-energy gamma rays is unlike anything seen before. What’s thrilling is that it exploded multiple times in one day, which challenges our current understanding of these phenomena.
Typically, GRBs occur when massive stars die and collapse into black holes or neutron stars. Antonio Martin-Carrillo, co-leader of the study and an astronomer at University College Dublin, described this GRB as “unlike any other seen in 50 years of GRB observations.”
Nasa’s Fermi Gamma-ray Space Telescope first detected GRB 250702B on July 2, 2025. Then, the Very Large Telescope (VLT) used its HAWK-I infrared camera to locate the event outside the Milky Way, later confirmed by the Hubble Space Telescope.
GRBs are extremely energetic, releasing energy comparable to what our sun will emit over 10 billion years, but GRB 250702B stood out because it lasted about a day. This duration is 100 to 1,000 times longer than most GRBs, as noted by Andrew Levan, a co-team leader from Radboud University.
When Fermi first observed this burst, it saw three emissions within hours. Data from the Einstein Probe X-ray space telescope later showed that the same source erupted the day before the initial detection. This unique characteristic makes GRB 250702B a “long-period repeating GRB,” something astronomers have never seen.
Experts are now pondering the mechanics behind this burst. Levan emphasized that if it’s from a massive star, “it is a collapse unlike anything we have ever witnessed.” Observations from the VLT revealed that GRB 250702B originated from another galaxy, indicating its power is much greater than previously thought. The team estimates that it lies billions of light-years away.
Finding the exact cause of this cosmic explosion remains challenging. One hypothesis involves a massive star collapsing in a way that causes a brief GRB, but it’s more complicated. Alternatively, if a star is disrupted by a black hole—known as a tidal disruption event (TDE)—this could potentially create a longer burst. However, this scenario doesn’t entirely align with the observed properties of GRB 250702B, suggesting something even more unusual is happening.
The astronomers are closely monitoring the aftermath using the VLT and the James Webb Space Telescope in hopes of uncovering the mysteries surrounding this unique blast.
The findings were published on August 29 in The Astrophysical Journal Letters. This discovery could change our understanding of the universe. It illustrates how much we still have to learn about gamma-ray bursts and the complex life cycles of stars.
