'Overweight' neutron star defies a black hole theory, say astronomers

Exclusive: Gamma-ray burst from colliding stars unexpectedly gave way to day-long sight of hypermassive body

Hannah Devlin Science correspondent
@hannahdev
Thu 10 Nov 2022 11.14 EST

An “overweight” neutron star has been observed by astronomers, who say the mysterious object confounds astronomical theories.

The hypermassive star was produced by the merger of two smaller neutron stars. Normally such collisions result in neutron stars so massive that they collapse into a black hole almost instantaneously under their own gravity. But the latest observations revealed the monster star hovering in view for more than a day before it faded out of sight.

“Such a massive neutron star with a long life expectancy is not normally thought to be possible,” said Dr Nuria Jordana-Mitjans, an astronomer at the University of Bath. “It is a mystery why this one was so long-lived.”

The observations also raise questions about the source of incredibly energetic flashes, known as short gamma-ray bursts (GRBs), that accompany neutron star mergers. These outbursts – the most energetic events in the universe since the big bang – were widely assumed to be launched from the poles of the newly formed black hole. But in this case, the observed gamma-ray burst must have emanated from the neutron star itself, suggesting that an entirely different process was at play.

More:
https://www.theguardian.com/science/2022/nov/10/overweight-neutron-star-defies-a-black-hole-theory-say-astronomers