One of the most extreme stars in the Milky Way is still strange.
Scientists have measured the mass of a neutron star called PSR J0952-0607, and found it to be the most massive neutron star ever discovered, weighing 2.35 times the mass of the Sun.
If true, this is very close to the theorized upper mass limit. about 2.3 solar masses For neutron starsThese ultra-dense stars represent an excellent laboratory for studying what we think is on the verge of collapse, in the hope of better understanding the strange quantum state of the matter they are made of.
“We know roughly how matter behaves at atomic density, such as in the nucleus of a uranium atom,” Astrophysicist Alex Filipenko said University of California, Berkeley.
“A neutron star is like a giant nucleus, but when you have one and a half solar masses of this stuff, which is about 500,000 Earth masses of nuclei that all stick together, it’s not quite that obvious. That’s how they’ll behave.”
Neutron stars are collapsed cores of massive stars that were between about 8 and 30 times the mass of the Sun, before they went supernova and blew most of their mass into space.
These cores, tending to be about 1.5 times the mass of the Sun, are among the densest objects in the universe; the only thing dense is a black hole,
Their mass is only packed over an area of 20 kilometers (12 mi) or more; At that density, protons and electrons can combine into neutrons. The only thing stopping this ball of neutrons from collapsing into a black hole is the force that would take them to occupy identical quantum states, described as the degeneration pressure.
In some ways this means that neutron stars behave like massive atomic nuclei. But what happens at this tipping point, where neutrons form exotic structures or blur into a soup of tiny particles, is hard to say.
PSR J0952-0607 was already one of the most interesting neutron stars in the Milky Way. It is known as a pulsar – a neutron star that is spinning very fast with jets of radiation emanating from the poles. As the star spins, these poles move away from the observer (us) as a cosmic lighthouse so that the star appears to pulsate.
These stars can be extremely fast, with their rotation rate on the scale of milliseconds. PSR J0952-0607 is the second fastest pulsar in the Milky Way, making mind-blowing rotations 707 times per second. (The fastest is only slightly faster, whose rotation rate 716 times per second,
It is also known as the “Black Widow” pulsar. The star is in a close orbit with a binary companion – so close that its enormous gravitational field pulls material from the companion star. This material forms an accretion disk that spins around and fills in the neutron star, much like water swirling around a creek. Angular momentum from the accretion disk is transferred to the star, increasing its spin rate.
A team led by Stanford University astrophysicist Roger Romani wanted to better understand how PSR J0952-0607 fits into the timeline of this process. The binary companion star is small, containing less than 10 percent of the Sun’s mass. The research team carefully studied the system and its orbit and used that information to derive a new, accurate measurement for the pulsar.
His calculations gave a result of 2.35 times the mass of the Sun, give or take 0.17 solar masses. Assuming a standard neutron star starts out with a mass of about 1.4 times the mass of the Sun, this means that PSR J0952-0607 has reduced an entire Sun’s worth of matter from its binary companion. This, the team says, is really important information about neutron stars.
“This provides some of the strongest constraints on the property of matter in manifolds of density observed in atomic nuclei. In fact, many other popular models of dense matter physics are excluded from this result,” Romani explained,
“A high maximum mass for neutron stars suggests that it is a mixture of nuclei and their dissolved up and down quarks all the way to the core. This does not include many proposed States of matterespecially those with foreign internal structures.”
Binary also shows a mechanism by which Pulsar, without binary peers, can have millisecond rotation rates. The companion of J0952-0607 is almost gone; Once it is completely consumed, the pulsar (if it does not exceed the upper mass limit and collapses further into a black hole) will maintain its extremely fast rotation speed for some time.
And it will be alone, just like all those different millisecond pulsars.
“As the companion star evolves and begins to form a red giant, the material expands to the neutron star, and that neutron star expands. By spinning, it now becomes incredibly active, and the particles from the neutron A wind of the star begins to blow out. That wind then hits the donor star and begins to separate the material, and over time, the mass of the donor star is reduced to the mass of the planet, and if even more As time passes, it completely disappears.” Filipenko said,
“So, this is how lone millisecond pulsars can be created. They weren’t alone to begin with – they had to be in a binary pair – but they slowly evaporated out to their peers, and they are now alone.”
research has been published in The Astrophysical Journal Letters,