These massive neutron stars had been around for less than the blink of an eye: ScienceAlert

These massive neutron stars had been around for less than the blink of an eye: ScienceAlert

These massive neutron stars had been around for less than the blink of an eye: ScienceAlert

Few things can be accomplished in a few hundred milliseconds. Still, for neutron stars seen in the reflections of two gamma-ray bursts, that’s more than enough time to teach us a thing or two about the life, death, and birth of black holes.

Sifting through an archive of high-energy flashes in the night sky, astronomers recently discovered patterns in the oscillations of light left behind by two different sets of colliding stars, indicating a pause in their journey of a super object. dense to an endless chasm of darkness.

This pause – somewhere between 10 and 300 milliseconds – is technically equivalent to two newly formed mega-sized neutron stars, which the researchers suspect are each spinning fast enough to briefly delay their inevitable fate as black holes.

“We know that short GRBs form when orbiting neutron stars crash together, and we know that they eventually collapse into a black hole, but the precise sequence of events is not well understood” , said Cole Miller, an astronomer at the University of Maryland. Park (UMCP) in the United States.

“We found these gamma ray patterns in two bursts observed by Compton in the early 1990s.”

For nearly 30 years, the Compton Gamma-Ray Observatory has circled the Earth and collected the brilliance of X-rays and gamma-rays that spilled out from distant cataclysmic events. This archive of high-energy photons contains a wealth of data on things like the collision of neutron stars, which release powerful pulses of radiation called gamma-ray bursts.

Neutron stars are veritable beasts of the cosmos. They pack twice the mass of our Sun inside a volume of space roughly the size of a small city. Not only does it do weird things to matter, forcing electrons to turn into protons to turn them into a thick layer of neutrons, but it can generate magnetic fields like nothing else in the Universe.

Spinned at high rotation, these fields can accelerate particles to ridiculously high speeds, forming polar jets that appear to “pulse” like supercharged headlights.

Neutron stars form when more ordinary stars (about 8 to 30 times the mass of our Sun) burn up the rest of their fuel, leaving a core about 1.1 to 2.3 solar masses in size, too cold to withstand to the compression of its own gravity.

Add a little more mass – for example by cramming two neutron stars together – and even the dull tremor of its own quantum fields can’t resist gravity’s urge to crush the living physics of the dead star. From a dense mass of particles, we get, well, whatever indescribable horror happens to be the heart of a black hole.

The basic theory on the process is pretty clear, setting general limits on how much a neutron star will weigh before it collapses. For cold, non-rotating balls of matter, that upper limit is just under three solar masses, but it also involves complications that could make the journey from neutron star to black hole less straightforward.

For example, early last year, physicists announced the sighting of a burst of gamma rays dubbed GRB 180618A, detected in 2018. In the afterglow of the burst, they detected the signature of a star at magnetically charged neutrons called a magnetar, one with a mass close to that of the two colliding stars.

Barely a day later, this heavy neutron star was no more, no doubt succumbing to its extraordinary mass and transforming into something from which not even light can escape.

How it managed to resist gravity for as long as it did is a mystery, though its magnetic fields may have played a role.

These two new discoveries could also provide some clues.

The most accurate term for the pattern observed in gamma-ray bursts recorded by Compton in the early 1990s is a quasi-periodic oscillation. The mix of frequencies rising and falling in the signal can be deciphered to describe the final moments of massive objects as they circle around and then collide.

From what the researchers can tell, the collisions each produced an object about 20% larger than the current record-holding heavy neutron star – a pulsar calculated to be 2.14 times the mass of our Sun. They were also twice the diameter of a typical neutron star.

Interestingly, the objects were spinning at an extraordinary rate of almost 78,000 times per minute, far faster than the record-breaking pulsar J1748-2446ad, which only manages 707 rotations per second.

The few rotations that each neutron star managed to complete in its brief split-second lifespan could have been powered by just enough angular momentum to fight against their gravitational implosion.

How this may apply to other neutron star mergers, further blurring the boundaries of stellar collapse and black hole generation, is a question for future research.

This research was published in Nature.

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