Observations of faint, planet-size star help weigh its millisecond pulsar companion. A dense, collapsed star has shredded and consumed nearly the entire mass of its stellar companion and, in the process, grown into the heaviest neutron star observed to date. It is spinning at 707 times per second making it one of the fastest spinning neutron stars in the Milky Way galaxy.

Heaviest Neutron Star Ever Discovered Is a “Black Widow” Devouring Its Mate

Weighing this record-setting neutron star, which tops the charts at 2.35 solar masses (the mass of our sun), helps astronomers understand the weird quantum state of matter inside these extremely dense objects. If they get much heavier than that, neutron stars collapse entirely and disappear as a black hole. We know roughly how matter behaves at nuclear densities, like in the nucleus of a uranium atom,” said Alex Filippenko, Distinguished Professor of Astronomy at the University of California, Berkeley. “A neutron star is like one giant nucleus, but when you have one-and-a-half solar masses of this stuff, which is about 500,000 Earth masses of nuclei all clinging together, it’s not at all clear how they will behave.”

According to Roger W. Romani, Stanford University astrophysics professor, neutron stars are incredibly dense, with 1 cubic inch weighing over 10 billion tons. This means that their cores are the densest matter in the universe short of black holes, which are impossible to study because they are hidden behind their event horizon. Therefore the neutron star, a pulsar designated PSR J0952-0607, is the densest object within sight of Earth.

The extreme sensitivity of the 10-meter Keck I telescope on Maunakea in Hawai’i was what made it possible to measure of the neutron star’s mass. It recorded a spectrum of visible light from the hotly glowing companion star, which is now reduced to the size of a large gaseous planet. Located in the direction of the constellation Sextans, the stars are about 3,000 light-years from Earth. Discovered in 2017, PSR J0952-0607 is referred to as a “black widow” pulsar. Their name is an analogy to the tendency of female black widow spiders to consume the much smaller male after mating. Hoping to establish the upper limit on how large neutron stars/pulsars can grow, Filippenko and Romani have been studying black widow systems for more than a decade.

“By combining this measurement with those of several other black widows, we show that neutron stars must reach at least this mass, 2.35 plus or minus 0.17 solar masses,” said Romani, who is a professor of physics in Stanford’s School of Humanities and Sciences and member of the Kavli Institute for Particle Astrophysics and Cosmology. “In turn, this provides some of the strongest constraints on the property of matter at several times the density seen in atomic nuclei. Indeed, many otherwise popular models of dense-matter physics are excluded by this result.” If 2.35 solar masses is close to the upper limit of neutron stars, the astronomers say, then the interior is likely to be a soup of neutrons as well as up and down quarks the constituents of normal protons and neutrons — but not exotic matter, such as “strange” quarks or kaons, which are particles that contain a strange quark.

Source: This news is originally published by scitechdaily

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