Astronomers detected on July 2, 2025 the longest gamma-ray burst ever recorded, called GRB 250702B. The event occurred in a distant galaxy, about 8 billion light years from Terra, when a black hole consumed a companion star. The explosion released jets of particles at almost the speed of light, generating gamma radiation for more than seven hours.
The initial signal was captured by NASA’s Telescópio Espacial of Raios Gama Fermi, which triggered automatic alerts to observatories around the world. Diferente of typical bursts, which last seconds or minutes, this one persisted for hours, with jet activity extending for days. Early detection enabled detailed analyses, revealing patterns of variability on one-second scales.
Light from the explosion traveled through the cosmos for 8 billion years before arriving at Terra, offering a glimpse of stellar events in an ancient era of the universe. Observatórios like Swift and James Webb confirmed their origin in a dusty galaxy, eliminating initial hypotheses of proximity to Via Láctea.
- The initial duration of gamma rays doubled the previous record of about three and a half hours.
- No sign of a supernova was observed, possibly obscured by galactic dust.
- The rapid variability suggests a black hole with a stellar mass, between 5 and 30 times that of Sol.
Early detection and global alerts
The Fermi Gamma-ray Instrumentos as well as Burst Alert Telescope of Swift and Konus-Wind confirmed the emission, which lasted for more than seven hours in total.
A day earlier, Einstein Probe recorded an increasing brightness in X-rays from the same direction, reversing the usual pattern of rapid decay. Essa anomaly led to an immediate mobilization of teams, including night observations at Very Large Telescope, at Chile. Initial data indicated a power equivalent to trillions of suns, but located billions of light years away.
International coordination allowed the precise triangulation of the position in the sky, close to a galactic spot. Imagens from
Mechanisms behind stellar destruction
Central hypotheses point to the merger of a stellar-mass black hole with a helium star, where the black hole penetrates and consumes the internal matter. Esse process releases energy in narrow jets, accelerated to 99.9% the speed of light, producing the observed gamma rays.
Another possibility involves an intermediate-mass black hole, thousands of times more massive than Sol, ripping apart a white dwarf that got too close. However, the one-second variability favors the stellar mass model, as larger holes would generate slower fluctuations. The absence of a supernova suggests that the explosion was confined or obscured.
Studies published in journals such as Astrophysical Journal Letters analyze the data, with ten articles generated in months. The prolonged duration challenges traditional models of collapses, where massive stars collapse directly into black holes.
The total energy released is estimated at 10^52 ergs, comparable to billions of supernovae combined, but channeled into directional jets.
Multiwave analysis reveals host galaxy
Telescópio Espacial Hubble confirmed the previously unknown host galaxy, a large, dusty structure 8 billion light years away. Imagens infrared images from James Webb, from October 5, 2025, positioned the burst at the upper edge of a dark dust band, ruling out a connection with the central supermassive black hole.
X-rays from Swift showed afterglow fading, with initial brightness reversed, while radio and optical picked up secondary emissions. Essa Multi-wave vision is crucial, as dust absorbs visible light but allows infrared to penetrate.
The galaxy exhibits high star formation, an environment conducive to binary systems of black holes and stars. Additional Observações radio waves, expected for months, will track residue from the event.
Debates over black hole masses
The length of days in the jets suggests exotic mechanisms beyond neutron star mergers or common stellar collapses. An intermediate-mass black hole would resolve gaps in the mass spectrum, but evidence for rapid variability skews toward stellar masses.
Teams differ: one favors a “helium merge”, with the black hole falling into the bloated star; another, intermediary tidal disruption. Nenhum model perfectly explains the absence of supernova, possibly due to dense dust.
Ten peer-reviewed papers, including Monthly Notices of the Royal Astronomical Society, discuss these scenarios. The resolution could redefine the formation of black holes in young galaxies.
Coordinated ground and space observations
The Very Large Telescope, in the desert of Atacama, captured the optical afterglow fading hours after the trigger. No Hemisfério Norte, Gemini North contributed infrared spectra, measuring redshift of z=0.6, confirming the distance.
Satellites like Psyche, en route to asteroid 16 Psyche, have detected secondary neutrons and gamma. Estação Espacial Internacional, via Monitor of All-sky X-ray Image, recorded peaks in soft X-rays.
This global network generated real-time data, with alerts via Gamma-ray Coordinates Network. Colaborações and Carnegie Mellon mobilized telescopes on holidays, ensuring continuous coverage.
Implications for modern astrophysics
GRB 250702B highlights gaps in relativistic jet models, with variability indicating particle acceleration on quantum scales. Estudos Futures will focus on radio waves to map the remnant, testing predictions of prolonged emission.
The detection reinforces the need for multi-messenger observatories, integrating gamma, X and gravitational. Eventos like this occur once a decade, but this one, with record duration, provides a benchmark for simulations.
Ongoing research with Event Horizon Telescope aims to image similar jets at fine angular resolutions.
Alternative scenarios under discussion
“Tidal micro-disruption” models propose small black holes orbiting stars, gradually falling in and consuming them from the inside out. Essa binary fusion explains sustained energy without immediate collapse.
Critics argue that mass intermediates, formed in dense clumps, fit better into the observed dust. Simulações numerical tests, run on supercomputers, test both, with results pending for 2026.
The current preference falls on stellar masses, in line with previous bursts, but the debate drives theoretical refinements.
Legacy of the burst for future missions
The event inspired proposals for upgrades to the Fermi and Swift, with sensors more resistant to saturation. Telescópio Espacial Nancy Grace Roman, scheduled for 2027, will prioritize searches for infrared afterglows.
International collaborations plan faster alert networks, integrating AI for data triage. Esse burst serves as a test for dark matter theories in galactic nuclei.
