Massive neutron stars have been around for less than the blink of an eye

(ORDO NEWS) — Not much can be done in a few hundred milliseconds. Nevertheless, for neutron stars visible in the glow of two gamma-ray bursts, this is more than enough time to teach us something about life, death, and the birth of black holes.

An archive of high-energy flares in the night sky, astronomers have recently discovered patterns in the fluctuations in light left behind by two different sets of colliding stars, indicating a pause in their journey from a super-dense object to an endless abyss of darkness.

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

“We know that short gamma-ray bursts are produced when neutron stars collide in orbit, and we know that they eventually collapse into a black hole, but the exact sequence of events is not well understood,” says Cole Miller, an astronomer at the University of Maryland, College Park (UMCP) in the USA.

“We and these pictures of gamma rays in two bursts observed by Compton in the early 1990s.”

For nearly 30 years, the Compton Gamma Ray Observatory has orbited the Earth and collected the aurora of X-rays and gamma rays emitted from distant cataclysms.

This archive of high-energy photons contains a wealth of data about things like colliding neutron stars that emit powerful bursts of radiation known as gamma-ray bursts.

Neutron stars are real space beasts. They pack twice the mass of our Sun into a volume of space roughly the size of a small city.

Not only does this do strange things to matter, causing electrons to turn into protons, turning them into heavy dust of neutrons, but it can also generate magnetic fields unlike anything else in the universe.

These fields rotate at high speed. can accelerate particles to ridiculously high speeds, creating polar jets that appear to “pulsate” like overloaded lighthouses.

Neutron stars form when more ordinary stars (about 8 to 30 times the mass of our Sun) burn out. the remnants of their fuel, leaving a core of 1.1 to 2.3 solar masses, too cold to resist being compressed by its own gravity.

Add a little more mass by squeezing two neutron stars together, for example and even the dim fluctuation of its own quantum fields cannot resist gravity’s urge to squeeze the living physics out of a dead star.

From a dense bunch of particles, we get an indescribable horror, which turns out to be the heart of a black hole.

The underlying theory behind this process is pretty clear and sets general limits on how heavy a neutron star can be before it collapses.

For cold non-rotating balls of matter, this upper bound is just under three solar masses, but it also implies complexities that could make traveling from a neutron star to a black hole less than easy.

For example, earlier last year, physicists announced the observation of a gamma-ray burst, called GRB 180618A, discovered back in 2018. to two colliding stars.

In less than a day, this heavy neutron star disappeared, no doubt succumbing to its extraordinary mass and becoming something that not even light can escape.

How it managed to resist gravity for so long remains a mystery, although its magnetic fields may have played a role.

These two new discoveries may also provide some clues.

A more accurate term for the pattern observed in the gamma-ray bursts recorded by Compton in the early 1990s is a quasi-periodic oscillation.

The combination of frequencies that rise and fall in the signal can be deciphered to describe the last moments in the motion of massive objects as they orbit each other and then collide.

The researchers can say that each collision produced an object about 20 percent larger than the current record holder for the mass of a neutron star, a pulsar with a mass of 2.14 times that of our Sun. In addition, they were twice the diameter of a typical neutron star.

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

The few revolutions that each neutron star has had time to make in its short life of a fraction of a second could be provided with sufficient angular momentum to combat their gravitational collapse.

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


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