Record-breaking Black Widow pulsar is the most massive neutron star

(ORDO NEWS) — One of the most extreme stars in the Milky Way just got crazier.

Scientists have measured the mass of the neutron star PSR J0952-0607 and found that it is the most massive neutron star. discovered yet, and their mass is 2.35 times the mass of the Sun.

If true, this is very close to the theoretical upper mass limit of about 2.3 solar masses for neutron stars, which is an excellent laboratory for studying these superdense stars, which we think are on the verge of collapse, in the hope of better understanding the strange quantum the state of matter of which they are composed.

“We roughly know how matter behaves at a density of nuclei, like in the nucleus of a uranium atom,” said astrophysicist Alex Filippenko from the University of California at Berkeley.

“A neutron star is like one giant nucleus, but when you have one-and-half of the solar mass of that material, which is about 500,000 Earth-mass nuclei tacked together, it’s completely unclear how y will behave.”

Neutron stars are the collapsing cores of massive stars that were between 8 and 30 solar masses before they went supernova and carried most of their mass into space.

These nuclei, about 1.5 times the mass of the Sun, are among the densest objects in the universe; the only thing denser is a black hole.

Their mass packs into a sphere only 20 kilometers (12 mi) or so in diameter; at such a density, protons and electrons can combine to form neutrons.

The only thing keeping this ball of neutrons from collapsing into a black hole is the force required for them to occupy the same quantum state, called degeneracy pressure.

In a sense, this means that neutron stars behave like massive atomic nuclei. But what happens at this tipping point, when neutrons form exotic structures or dissolve into a soup of smaller particles, is hard to say.

PSR J0952-0607 was already one of the most interesting neutron stars in the Milky Way. Path. This is what is known as a pulsar – a neutron star that rotates very quickly, and the poles emit jets of radiation.

As the star rotates, these poles sweep past the observer (us) like a cosmic beacon, so that the star appears to pulsate.

These stars can be insanely fast, spinning in milliseconds. PSR J0952-0607 is the second fastest pulsar in the Milky Way, spinning at 707 revolutions per second. (The fastest one is only slightly faster, spinning 716 times per second.)

This is also what is known as a “black widow” pulsar. The star is in a close orbit with a binary companion so close that its huge gravitational field pulls material away from the companion star.

This material forms an accretion disk that rotates and feeds the neutron star like water spinning around a drain. The angular momentum from the accretion disk is transferred to the star, which leads to an increase in its rotation speed.

A team led by Stanford University astrophysicist Roger Romani wanted to better understand how PSR J0952-0607 fits into the timeline for this process.

The binary companion star is tiny, less than 10 percent of the mass of the Sun. The research team carefully studied the system and its orbit and used this information to obtain new accurate measurements of the pulsar.

Their calculations gave a result of 2.35 times the mass of the Sun, plus or minus accept 0.17 solar masses.

Assuming that the initial mass of a standard neutron star is about 1.4 times the mass of the Sun, this means that PSR J0952-0607 sucked the equivalent of all solar matter from its binary companion. The team says this is really important information about neutron stars.

“This provides some of the strongest constraints on the property of matter several times the density seen in atomic nuclei. Indeed, many others. This result rules out popular models of dense matter physics,” Romani explained.

“The high maximum mass of neutron stars suggests that they are a mixture of nuclei and their dissolved up and down quarks all the way to the nucleus. This rules out many putative states of matter, especially those with exotic internal compositions.”

The binary system also shows the mechanism by which isolated pulsars without binary companions can have millisecond spin rates.

Satellite J0952-0607 has almost disappeared; once it is completely consumed, the pulsar (unless it rolls over the upper mass limit and crashes further into the black hole) will maintain its insanely fast spin rate for some more time.

And it will be alone, just like all other isolated millisecond pulsars.

“As the companion star evolves and starts to become a red giant, material flows to the neutron star and that spins the neutron star. particles start to fly out of the neutron star.

Then this wind hits the donor star and begins to rip off the matter, and over time, the mass of the donor star decreases to the mass of the planet, and if even more time passes, then it disappears altogether, ”Filippenko. said.

“So, this is how single millisecond pulsars could form. They weren’t single to begin with – they were supposed to be in a binary pair – but they gradually vaporized their companions and now they’re single.”

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