The cosmic gluttonous ‘black widow’ is the heaviest known neutron star

By Will Dunham

WASHINGTON (Reuters) – Astronomers have observed the most massive known example of an object called a neutron star, classified as a “black widow” that has become particularly heavy by swallowing up most of the mass of a stellar companion trapped in an unhappy cosmic marriage.

The researchers said the neutron star, which is spinning wildly at 707 times per second, has a mass about 2.35 times that of our sun, putting it perhaps at the maximum possible for such objects before they don’t collapse to form a black hole.

A neutron star is the collapsed compact core of a massive star that exploded as a supernova at the end of its life cycle. The one described by the researchers is a type of highly magnetized neutron star called a pulsar that releases beams of electromagnetic radiation from its poles. As it spins, these beams appear from the vantage point of an observer on Earth to pulse – similar to the rotating light of a lighthouse.

Only one other neutron star is known to spin faster than this one.

“The heavier the neutron star, the denser the material in its core,” said Roger Romani, director of the Center for Space Science and Astrophysics at Stanford University and co-author of the research published this week in Astrophysical Journal Letters.

“So, as the heaviest known neutron star, this object exhibits the densest material in the observable universe. If it were heavier, it should collapse into a black hole, and then the substance inside would be behind the event horizon, forever isolated from observation,” Romani added.

The event horizon of a black hole is the point of no return beyond which everything, including light, is sucked irretrievably.

“Since we don’t yet know how matter functions at these densities, the existence of this neutron star is an important probe of these physical extremes,” Romani said.

The neutron star, residing in our Milky Way galaxy in the direction of the constellation Sextans and officially named PSR J0952-0607, is located about 20,000 light-years from Earth, Romani said. A light year is the distance light travels in one year, 5.9 trillion miles (9.5 trillion km). The researchers studied it using the Keck I telescope in Hawaii.

Stars that are about eight times or more the mass of the sun convert hydrogen into heavier elements by thermonuclear fusion in their cores. When they accumulate about 1.4 times the mass of our sun in iron, this core collapses into a neutron star with a diameter about the size of a city, the rest being blown away by the explosion of the supernova.

Its material is so compact that an amount the size of a sugar cube would outweigh Mount Everest.

This neutron star inhabits what is called a binary system, orbiting with another star. The neutron star is a kind nicknamed a “black widow,” named for female black widow spiders that eat their male partners after mating.

It was apparently born with the usual mass of a neutron star, about 1.4 times that of our sun, but its gravitational pull stole material from its companion star, allowing it to grow to a mass seemingly upper limit before physics dictates a collapse. in a black hole, the densest of all known objects.

Its companion star has been nearly stripped bare, losing perhaps 98% of its mass to Black Widow, leaving it about 20 times the mass of our solar system’s largest planet, Jupiter – a far cry from its original size.

“It swallowed near a full mass sun without yet becoming a black hole, so it should be just on the verge of black hole collapse,” Romani said.

(Reporting by Will Dunham; Editing by Lisa Shumaker)

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