Written by Will Dunham
WASHINGTON (Reuters) – Astronomers have observed the largest known example of an object called a neutron star, one of the examples classified as a “black widow” gaining particularly significant weight by devouring most of the mass of a companion star trapped in an unhappy cosmic marriage. .
The neutron star, which rotates at a speed of 707 times per second, has a mass about 2.35 times greater than the mass of our sun, the researchers said, possibly putting it as far as possible for such objects before they 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. What the researchers describe is a highly magnetized type of neutron star called a pulsar that shoots beams of electromagnetic radiation from its poles. As they rotate, these beams appear from an observer’s perspective on Earth to pulse – similar to the rotation of a lighthouse light.
Only one neutron star is known to spin faster than this one.
“The heavier a neutron star is, the denser the material in its core,” said Roger Romani, director of the Stanford University Center for Space Science and Astrophysics and one of the authors of the research published this week in Astrophysical Journal Letters.
“Like the heaviest known neutron star, this object presents the densest material in the observable universe. If it was heavier, it should collapse into a black hole, and then the things inside it would be behind the event horizon, forever closed from any observation.”
The event horizon of a black hole is the point of no return beyond which anything including light is irreversibly absorbed.
“Since we do not yet know how matter operates at these densities, the presence of this neutron star is an important probe of these extreme physical phenomena,” Romani said.
Roman said that the neutron star, located 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. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). The researchers studied this using the Keck I telescope in Hawaii.
Stars more than eight times the mass of the Sun convert hydrogen into heavier elements through thermonuclear fusion in their cores. When a mass of iron 1.4 times the mass of our Sun accumulates, that core collapses into a neutron star only about the size of a city in diameter, and the rest explodes in a supernova explosion.
Its substance is so compact that an amount the size of a sugar cube exceeds that of Mount Everest.
This neutron star inhabits the so-called binary system, in orbit with another star. A neutron star is of the type called a “black widow,” and was named in honor of a female black widow spider who eats her male partners after mating.
It was apparently born with the usual mass of a neutron star, about 1.4 times the mass of our sun, but its gravity pulls matter from its companion star, enabling it to grow to a mass seemingly at its maximum before physics dictated the collapse. In a black hole, it is the densest of all known objects.
Its companion star has been nearly stripped naked, losing perhaps 98% of its mass to Black Widow, leaving it about 20 times the mass of the largest planet Jupiter in our solar system – a far cry from its original size.
“You’ve swallowed up nearly the mass of a whole sun without having yet turned into a black hole,” Roman said. “So you should be on the verge of black hole collapse.”
(Reporting by Will Dunham; Editing by Lisa Shumaker)
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