NASA's Fermi Spots 'Fizzled' Burst from Collapsing Star

On Aug. 26, 2020, NASA’s Fermi Gamma-ray Space Telescope detected a pulse of high-energy radiation that turned out to be one for the record books – the shortest gamma-ray burst (GRB) caused by the death of a massive star ever seen. GRBs are the most powerful events in the universe. Astronomers classify them as long or short based on whether the event lasts for more or less than two seconds. They observe long bursts in association with the demise of massive stars, while short bursts have been linked to a different scenario. Named GRB 200826A, the event is definitely a short-duration GRB, but other properties point to its origin from a collapsing star. When a star much more massive than the Sun runs out of fuel, its core suddenly collapses and forms a black hole. As matter swirls toward the black hole, some of it escapes in the form of two powerful jets that rush outward at almost the speed of light in opposite directions. Astronomers only detect a GRB when one of these jets happens to point almost directly toward Earth. Each jet drills through the star, producing a pulse of gamma rays – the highest-energy form of light – that can last up to minutes. Following the burst, the disrupted star then rapidly expands as a supernova. To prove the blast came from a dying star, a team led by Tomás Ahumada, a doctoral student at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland, searched for the GRB’s fading afterglow and the emerging light of the supernova explosion that followed. GRB 200826A was a sharp blast of high-energy emission about a second long when it was detected by Fermi’s Gamma-ray Burst Monitor. NASA’s Wind and Mars Odyssey missions also saw it, as did ESA's (the European Space Agency’s) INTEGRAL satellite, which enabled astronomers to narrow the burst's location in the sky. They quickly located the afterglow using the Zwicky Transient Facility (ZTF) at Palomar Observatory. Twenty-eight days after the burst, the team detected the light of a supernova in the burst's host galaxy, proving the blast came from the demise of a massive star. The astronomers describe the GRB as a fizzle, where weak jets lasted just long enough to breach the star's surface before shutting down. If the jets had been any weaker, the burst might not have occurred at all. Music Credit: "Inducing Waves" from Universal Production Music Credit: NASA's Goddard Space Flight Center Scott Wiessinger (KBRwyle): Producer Francis Reddy (University of Maryland College Park): Lead Science Writer Chris Smith (KBRwyle): Lead Animator Barb Mattson (University of Maryland College Park): Narrator Tomás Ahumada (University of Maryland College Park): Scientist Tomás Ahumada (University of Maryland College Park): Narrator (Spanish)