AssetID: 55341343
Headline: RAW VIDEO: Mysterious gamma-ray explosion in deep space is longest ever recorded
Caption: Astronomers have recorded a giant explosion the likes of which they have never seen before. The event was the longest gamma-ray burst (GRB) ever observed - a colossal cosmic blast that continued for more than seven hours and is challenging existing theories of physics. Gamma-ray bursts are the most energetic explosions in the Universe since the Big Bang and are detected, on average, about once a day. Most last only seconds or minutes. But on 2 July 2025, NASA’s Fermi Gamma-ray Space Telescope detected something very different: a burst that kept flaring repeatedly for hours. Named GRB 250702B, it is now the longest-duration of these events ever recorded. After the initial alert from Fermi, astronomers around the world rapidly turned their telescopes towards the source to capture its fading afterglow and determine its origin. Observations across multiple wavelengths revealed that the burst came from a distant galaxy far beyond the Milky Way. Infrared data from the European Southern Observatory’s Very Large Telescope confirmed that the explosion was extragalactic, settling early uncertainty about its location. A team led by Jonathan Carney, a graduate student at the University of North Carolina at Chapel Hill, coordinated follow-up observations using some of the world’s most powerful ground-based telescopes, including the NSF Víctor M. Blanco 4-metre Telescope in Chile and the twin 8.1-metre Gemini North and South telescopes. The observations began around 15 hours after the burst was first detected and continued for more than two weeks. Their findings were published on 26 November in The Astrophysical Journal Letters. “The ability to rapidly point the Blanco and Gemini telescopes on short notice is crucial to capturing transient events such as gamma-ray bursts,” says Carney. “Without this ability, we would be limited in our understanding of distant events in the dynamic night sky.” The team used a range of instruments, including the Dark Energy Camera on the Blanco telescope and the Gemini Multi-Object Spectrographs on both Gemini telescopes. They found that GRB 250702B was extremely difficult to observe in visible light, largely because it is shrouded in dust — both in our own galaxy and, more significantly, in its host galaxy. Even with Gemini North, nearly two hours of observations were needed to detect the faint glow of the host galaxy. By combining these data with further observations from the Keck, Magellan Baade and Fraunhofer telescopes, as well as archival data from the Very Large Telescope, NASA’s Hubble Space Telescope, and X-ray and radio observatories, the researchers compared the observations with theoretical models. Their analysis suggests the initial burst was produced by a narrow, ultra-fast jet of material travelling at least 99% of the speed of light - known as a relativistic jet - slamming into the surrounding environment. The host galaxy appears to be unusually massive for a GRB and rich in dust, indicating the explosion occurred in a dense and obscured region. Out of roughly 15,000 gamma-ray bursts observed since the phenomenon was identified in 1973, only a handful approach the duration of GRB 250702B. Even so, this event does not fit neatly into any known category. Scientists are now considering several possible explanations, including a black hole plunging into a helium-rich star, a so-called micro–tidal disruption event involving a star or planet-sized object, or a star being torn apart by an elusive intermediate-mass black hole. If the latter is correct, it would be the first time such a black hole has been seen producing a relativistic jet while consuming a star. More observations will be needed to pin down the exact cause, but astronomers say the data so far are consistent with these unusual scenarios. “This work presents a fascinating cosmic archaeology problem in which we’re reconstructing the details of an event that occurred billions of light-years away,” says Carney. “The uncovering of these cosmic mysteries demonstrates how much we are still learning about the Universe's most extreme events and reminds us to keep imagining what might be happening out there.”
Keywords: feature,photo,video,astronomy,science,space
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