Heaviest neutron star forms after engulfing companion star

Heaviest neutron star forms after engulfing companion star
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Dubbed a neutron star, the dense, collapsed remnants of a massive star weigh more than twice the mass of our Sun, making it the heaviest neutron star known to date. The object rotates 707 times per second, making it also one of the fastest rotating neutron stars in the Milky Way.

The neutron star is known as the black widow because it is known in a manner similar to these arachnids female spiders, which consume much smaller male mates after mating, the star has shredded and engulfed nearly the entire mass of its companion.

This stellar feast has allowed the Black Widow to become the heaviest neutron star observed to date.

Astronomers have been able to weigh the star, designated PSR J0952-0607 with the sensitive Keck telescope at the WM Keck Observatory on Maunakea in Hawaii.

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The observatory’s Low Resolution Imaging Spectrometer recorded visible light from the ragged companion star, which was glowing from its high heat.

The companion star is now about the size of a large gas planet, or 20 times the mass of Jupiter. The side of the companion star that faces the neutron star is heated to 10,700 degrees Fahrenheit (5,927 degrees Celsius) — hot and bright enough to be seen with a telescope.

Neutron star cores are the densest matter in the universe outside of black holes, and a neutron star’s 1 cubic inch (16.4 cubic centimeters) weighs more than 10 billion tons, according to study author Roger W. Romani, a professor of physics at Stanford University in California.

This particular neutron star is the densest object in sight of Earth, according to the researchers.

Astronomers observed a faint star (green circle) stripped of almost all of its mass by an invisible neutron star.  The striped star is much fainter and smaller than a normal star (above).

“We know roughly how matter behaves at nuclear density, like in the nucleus of a uranium atom,” study co-author Alex Filippenko said in a statement. Filippenko has the dual titles of Professor of Astronomy and distinguished professor of Physical Sciences at the University of California, Berkeley.

“A neutron star is like a giant core, but when you have a solar mass and a half of this stuff, which is about 500,000 Earth masses of cores all stuck together, it’s not at all clear how they’re going to behave.”

A neutron star like PSR J0952-0607 is called a pulsar because the object acts like a cosmic beacon as it spins, periodically emitting light by radio waves, X-rays, or gamma rays.

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Normal pulsars spin and blink about once a second, but this one pulses hundreds of times a second. This is because the neutron star gains more energy as it sheds material from the companion star.

“In a case of cosmic ingratitude, the Black Widow pulsar, having engulfed much of its mate, is now heating and vaporizing the companion to planetary masses and possible complete annihilation,” Filippenko said.

astronomers discovered first the neutron star in 2017, and Filippenko and Romani have studied similar black widow systems for more than a decade. They tried to understand how big neutron stars can get. When neutron stars get too heavy, they collapse and become black holes.

The star PSR J0952-0607 has 2.35 times the mass of the Sun, which is now considered the upper limit for a neutron star, the researchers said.

“We can continue to search for black widows and similar neutron stars that are slipping even closer to the edge of the black hole. But if we don’t find any, that reinforces the argument that 2.3 solar masses is the true limit beyond which they become black holes, Filippenko said.

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