A ‘Black Widow’ Cannibal Star That Rotates 707 Times Per Second Could Solve Black Hole Mystery

Astronomers have found a neutron star that spins an astonishing 707 times per second—and it has instantly become the densest object we can see from Earth. It could help solve the mystery behind when a collapsed star becomes a black hole.

One the fastest spinning neutron stars in the Milky Way galaxy, PSR J0952-0607 was spotted from the W. M. Keck Observatory on Maunakea, Hawaii. It’s about 3,000 light years from Earth in the direction of the constellation Sextan.

A neutron star is the dense collapsed core of a massive star that’s exploded as a supernova. PSR J0952-0607 is also a pulsar, which is what astronomers called neutron stars that rotate and emit pulses of radiation as radio waves, X-rays or even gamma rays that telescopes on Earth can sometimes detect.

In this case dense really does mean dense. In fact, in a neutron star a single cubic inch weighs over 10 billion tons. In total PSR J0952-0607 weighs in at more than twice the mass of the Sun. It was first discovered in 2017.

It’s so dense, in fact, that it could soon collapse entirely and disappear as a black hole, which could give it a special importance to astronomers. Black holes are even denser, they can’t be studied because of their event horizon.

Published in The Astrophysical Journal Letters today the new study reveals that PSR J0952-0607 got to be so dense and spin so fast by shredding and evaporating away its companion star. Hence it being referred to as a “black widow” pulsar (female black widow spiders often eat the much smaller male after mating).

PSR J0952-0607 can be weighed because its companion star—which is now only 20 times the mass of Jupiter—is so small, yet bright enough to detect.

“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,” said Alex Filippenko, Distinguished Professor of Astronomy at the University of California, Berkeley, who has been studying “black widow” systems for more than a decade.

Such “lone millisecond pulsars” like PSR J0952-0607 appear to have a very odd origin story. The paper suggests that all pulsars that pulse as rapidly must be, or have been, in a binary pair.

“As the companion star evolves and starts becoming a red giant, material spills over to the neutron star, and that spins up the neutron star,” said Filippenko. By spinning up, it now becomes incredibly energized. A wind of particles starts coming out from the neutron star. “That wind then hits the donor star and starts stripping material off, and over time, the donor star’s mass decreases to that of a planet, and if even more time passes, it disappears altogether,” said Filippenko.

This analysis of PSR J0952-0607 could also help with work on how and when black holes form.

“We can keep looking for black widows and similar neutron stars that skate even closer to the black hole brink,” said Filippenko. “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.”

The research is also right at the limit of what the Keck telescope can do, said the authors of the paper, so more research will probably have to wait until the Extremely Large Telescope and the Thirty Meter Telescope see “first light” in the next decade.

Wishing you clear skies and wide eyes.