A surprisingly short gamma-ray burst has astronomers rethinking what triggers these celestial cataclysms.
The Fermi Gamma-ray Space Telescope detected a single-second-long blast of gamma rays, dubbed GRB 200826A, in August 2020. Such fleeting gamma-ray bursts, or GRBs, are usually thought to originate from star smashups. But a better check out the burst revealed that it came from the implosion of a huge star’s core.
In this scenario, the core of a star collapses into a compact object, like a region, that powers high-speed particle jets. Those jets punch through the remainder of the star and radiate powerful gamma rays before the outer layers of the star explode during a supernova. That process is usually thought to supply longer GRBs, lasting quite two seconds.
Discovering such a quick gamma-ray burst from a stellar explosion suggests that some bursts previously classified as stellar mergers may very well be from the deaths of massive stars, researchers report online July 26 in two studies in Nature Astronomy.
The first clues about GRB 200826A’s origin came from the burst itself. The wavelengths of sunshine and amount of energy released within the burst were more almost like collapse-related GRBs than collision-produced bursts, Bing Zhang, an astrophysicist at the University of Nevada, Las Vegas, and colleagues report. Plus, the burst hailed from the center of a star-forming galaxy, where astronomers expect to seek out collapsing massive stars, but not star mergers — which are generally found on the fringes of tranquil galaxies.
Another group, led by astronomer Tomás Ahumada-Mena of the University of Maryland in College Park, looked for the supernova that’s expected to follow a GRB produced by a collapsing star. Using the Gemini North Telescope in Hawaii to watch GRB 200826A’s host galaxy, the team was ready to detect the telltale infrared of the supernova. The burst may are so brief because its jets had just barely punched through the surface of the star before they faded and therefore the star blew up, Ahumada-Mena says.