Unlike most gamma-ray bursts, which are caused by exploding massive stars or the chance mergers of neutron stars, a long gamma-ray burst event dubbed GRB 191019A came from the collision of stars or stellar remnants in the jam-packed environment surrounding a supermassive black hole at the core of an ancient galaxy, suggests an analysis of data from the Gemini South telescope, part of the International Gemini Observatory operated by NSF’s NOIRLab.
Most stars in the Universe die in predictable ways, depending on their mass.
Relatively low-mass stars like our Sun slough off their outer layers in old age and eventually fade to become white dwarf stars.
More massive stars burn brighter and die sooner in cataclysmic supernova explosions, creating ultradense objects like neutron stars and black holes.
If two such stellar remnants form a binary system, they also can eventually collide.
New research, however, points to a long-hypothesized, but never-before-seen, fourth option.
“Our new results show that stars can meet their demise in some of the densest regions of the Universe where they can be driven to collide,” said Radboud University astronomer Andrew Levan.
“This is exciting for understanding how stars die and for answering other questions, such as what unexpected sources might create gravitational waves that we could detect on Earth.”
Ancient galaxies are long past their star-forming prime and would have few, if any, remaining giant stars, the principal source of long gamma-ray bursts (GRBs).
Their cores, however, are teeming with stars and a menagerie of ultra-dense stellar remnants, such as white dwarf stars, neutron stars, and black holes.
Astronomers have long suspected that in the turbulent beehive of activity surrounding a supermassive black hole, it would only be a matter of time until two stellar objects collide to produce a GRB. Evidence for that type of merger, however, has been elusive.
The first hints that such an event had occurred were…
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