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‘Impossible’ neutron stars could explain strange flashes | Space

The oscillating frequencies of two short gamma-ray bursts are the best evidence yet for the formation of ‘impossible’ hypermassive neutron stars that can briefly defy gravity before collapsing to form a black hole.

A neutron star forms when a large star runs out of fuel and explodes, leaving behind a super-dense remnant that can pack the mass of the sun into the space of a city. Usually, a neutron star can only contain a bit more than two times the mass of the sun before it undergoes gravitational collapse to form a black hole. However, when two regular neutron stars in a binary system merge, their combined mass can exceed this limit — but only briefly, and the stage is difficult to spot.

“We need to start with two light neutron stars in the binary in order to form a hypermassive neutron star, otherwise there would be a direct collapse to a black hole,” Cecilia Chirenti, who led the research, told Space.com. Chirenti is an astrophysicist at the University of Maryland, NASA’s Goddard Space Flight Center in Maryland and the Center for Mathematics, Computation and Cognition at the Federal University of ABC in Brazil.  …