Astronomers have detected a remarkable space signal pulsating towards Earth, lasting an unprecedented seven hours. This extraordinary event, cataloged as GRB 250702B, has captivated astrophysicists worldwide, challenging their understanding of cosmic phenomena. The signal, initially observed in mid-2025, broke records for gamma-ray burst duration, leaving scientists intrigued and eager to unravel its mysteries.
The burst's prolonged nature sets it apart from typical gamma-ray bursts (GRBs), which usually release their energy within minutes. GRB 250702B's extended duration of approximately 25,000 seconds far surpasses previous records, prompting a global response from research institutions. Within hours of the initial alert, data-sharing channels across NASA, the European Space Agency (ESA), and various research centers sprang into action, underscoring the significance of this discovery.
Eliza Neights, a researcher at NASA's Goddard Space Flight Center, described the detection process in an interview with BBC Sky at Night Magazine. Neights explained that the gamma-ray pattern was initially interpreted as three separate events but later reclassified as a single, sustained burst from a consistent origin. This reclassification highlights the complexity of the event and the need for further investigation.
The five observatories involved, including instruments from NASA, ESA, and partner institutions, collaborated to analyze the signal's characteristics. Their combined light curve data revealed sustained energy release, suggesting that GRB 250702B may have originated from a fundamentally different progenitor than typical GRBs. However, no direct redshift measurement has been published, and the host galaxy remains unidentified.
The anomaly of GRB 250702B has sparked intriguing theories. One hypothesis involves a black hole consuming a helium star, a scenario that doesn't fit neatly into the conventional classification of short-duration (under 2 seconds) and long-duration (2 to 300 seconds) GRBs. The research team exploring this possibility identified a helium star merger scenario, where a stellar-mass black hole in close orbit with a helium-rich star accretes material at a high rate, potentially generating a long-lived relativistic jet and observable gamma-ray emissions for hours.
While this scenario remains theoretical, it is considered the most viable explanation consistent with the data gathered. It opens up new avenues for understanding stellar evolution in binary systems, particularly those involving black holes and evolved stars. However, it also highlights the limitations of current gamma-ray observatories, which may be missing more of these prolonged bursts due to their detection criteria favoring brief, high-intensity flashes.
To address this, NASA's team is integrating long-duration burst criteria into mission planning for the upcoming Compton Spectrometer and Imager (COSI), scheduled for launch in 2027. COSI will enhance sensitivity to low-intensity, extended emissions, ensuring a more comprehensive detection of such phenomena. The 2025 event serves as a reference scenario for algorithm testing and detection model updates, paving the way for a deeper understanding of these extraordinary cosmic occurrences.
