Black Widow Named Heaviest Neutron Star to Date Through Keck I Telescope

Scientists discovered that the millisecond pulsar, Black Widow, is spinning 707 times per second, making it one of the fastest spinning neutron stars in the Milky Way galaxy. Based on the research, it consumed nearly the entire mass of its companion star, making it the densest and heaviest neutron star.

How are Neutron Stars Formed?

According to Roger W. Romani, an astrophysics professor at Stanford University, neutron stars are so dense that one cubic inch weighs more than 10 billion tons.

Astronomers generally believe that when a star with a core mass greater than 1.4 solar masses collapses at the end of its life, it produces a dense, compact object with an interior under such intense pressure that all atoms are smashed together to form a sea of neutrons and quarks.

These neutron stars are born spinning and, albeit too dim to be seen in visible light, expose themselves as pulsars, releasing light beams, waves, and rays that flash on Earth as they spin, much like a lighthouse's rotating beam.

Alex Filippenko, Distinguished Professor of Astronomy at the University of California, Berkeley, explained that a neutron star is like one giant nucleus. However, it is unclear how it will behave when it has one-and-a-half solar masses, which is about 500,000 Earth masses of nuclei clinging together.

Black Widow Pulsar Star Features

Black widow pulsar was discovered in 2017. The name refers to the tendency of female black widow spiders to swallow the much smaller male after mating. The stars' 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. The neutron star is identified as a pulsar known as PSR J0952-0607. The data was published in the Astrophysical Journal Letters.

The neutron star's mass was determined through the high sensitivity of the 10-meter Keck I telescope in Maunakea, Hawaii. The telescope could record a spectrum of visible light from the blazing companion star, which had shrunk to the size of a big gaseous planet. The stars are approximately 3,000 light years from Earth in the Sextans constellation.

The researchers utilize the Keck I telescope six times in the previous four years, using the Low-Resolution Imaging Spectrometer in 15-minute chunks to catch the faint companion at certain points in its 6.4-hour orbit around the pulsar. By comparing the spectra to those of similar sun-like stars, they could determine the companion star's orbital velocity and calculate the neutron star's mass.

They have looked at approximately a dozen black widow systems so far, but only six of them had partner stars luminous enough to compute mass. All of the neutron stars involved were less massive than the pulsar PSR J0952-060.

"We can keep looking for black widows and similar neutron stars that skate even closer to the black hole brink. But if we don't find any, it tightens the argument that 2.3 solar masses is the true limit, beyond which they become black holes," Filippenko said.

Romani added that it is right at the limit of what the Keck telescope can do, so barring fantastic observing conditions, tightening the measurement of PSR J0952-0607 likely awaits the 30-meter telescope era.

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