Besides the Big Bang itself, gamma ray bursts (GRBs) are the most energetic events in the universe. Astronomers knew of a few mechanisms that can produce them, but now an oddball GRB hints at a brand new origin – a stellar “demolition derby.”
As the name suggests, gamma ray bursts are intense pulses of gamma radiation that fire off in beams like a lighthouse. The most common cause is when a massive star collapses into a black hole, but they also occur from collisions between binary stellar remnants – like neutron stars or white dwarfs – or maybe when stars are swallowed up by black holes. But a recent detection appears to have come from a previously unknown source.
This oddball was detected on October 19, 2019, and as such was designated GRB 191019A. It lasted for over a minute, classifying it as a long GRB, which are usually created by collapsing stars. However, the astronomers saw no flash of light that would mark the supernova expected from the collapse of a star.
Its location hinted at an alternative origin. GRB 191019A was traced to near the center of an ancient galaxy, where there are often a million or more stars crammed into a relatively small region of space. With a supermassive black hole swirling everything around, collisions between stars become increasingly likely, creating what the researchers describe as a stellar “destruction derby.” And this is what produces GRBs like the one detected here.
“The discovery of these extraordinary phenomena within dense stellar systems, especially those encircling supermassive black holes at the cores of galaxies, is undeniably exciting,” said Giacomo Fragione, co-author of the study. “This remarkable discovery grants us a tantalizing glimpse into the intricate dynamics at work within these cosmic environments, establishing them as factories of events that would otherwise be deemed impossible.”
The team says that GRBs produced this way might be pretty common occurrences, but astronomers could be missing them because those environments are often cloaked in dust and gas. Finding more would be valuable for learning about the deaths of stars, and the dynamics of galaxies.
The research was published in the journal Nature Astronomy.
Source: Northwestern University