Fastest Spinning Neutron Star Just Found, But Its Spin Makes No Sense

Summary

A new discovery has revealed an extremely fast-spinning neutron star, rotating at 716 times per second (716 Hz), almost matching the record set by a similar object in 2004. This neutron star, part of an X-ray binary system, spins far beyond the expected limit of 350 Hz, raising questions about the theoretical maximum speed for neutron stars. With its unique characteristics, including the shortest orbital period of any X-ray binary, the system challenges current astrophysical models. Researchers are eager to study these extreme pulsars to understand whether this spin rate is a fundamental limit or a unique anomaly.

Takeaways

• 😀 The discovery of a neutron star spinning at 716 Hz challenges our understanding of neutron star rotation speeds, making it one of the fastest spinning objects observed.
• 😀 This neutron star is part of the X-ray binary system 4U 1820-30 in the globular cluster NGC 6624, which contains both a neutron star and a white dwarf orbiting extremely closely with a period of only 11 minutes.
• 😀 The system exhibits 'burst' behavior with regular thermonuclear explosions, which led to the accidental discovery of the neutron star's rapid spin rate.
• 😀 The frequency of 716 Hz was found to be the same as another pulsar, PSR G748, discovered over two decades ago, raising questions about why two objects share the same spin despite different ages and locations.
• 😀 Neutron stars are expected to spin up to about 350 times per second due to the accretion of mass, but the observed spin rate of 716 Hz far exceeds this typical limit.
• 😀 Theoretical models suggest neutron stars would break apart if they spin faster than around 1500 Hz, but gravitational waves would cause deceleration, preventing such high speeds.
• 😀 Despite theoretical limits, the discovery of two pulsars with nearly identical spin rates suggests the possibility of an unknown upper limit for neutron star rotation, likely between 700-730 Hz.
• 😀 Another pulsar, PSR G952-0607, spins at 707 Hz, reinforcing the idea of a natural upper limit for neutron star rotation speeds.
• 😀 These pulsars’ rapid spin rates may be a result of a balance between acceleration due to mass accretion and deceleration due to gravitational radiation.
• 😀 The unusual clustering of pulsars spinning at around 716 Hz could point to a new discovery about neutron star physics, potentially revealing the ultimate limit for their spin rates.

Q & A

What is the key discovery mentioned in the video?

The key discovery is a neutron star spinning at 716 Hertz, making it one of the fastest-spinning objects ever observed. This discovery raises questions about the maximum spin rate for neutron stars.

What is unique about the X-ray binary system in NGC 6624?

The X-ray binary system in NGC 6624 is unique because it contains a neutron star and a white dwarf that orbit extremely closely, with an orbital period of just 11 minutes, the shortest known for such a system.

How do neutron stars accelerate their spin rate?

Neutron stars accelerate their spin rate through a process called accretion, where they capture mass from a companion star. The transfer of angular momentum during accretion causes the neutron star to spin faster.

What is the theoretical limit for the spin rate of a neutron star?

Theoretical models suggest that the spin rate of a typical neutron star should not exceed 350 rotations per second, as any higher speed would likely break the star apart due to centrifugal forces.

Why is the 716 Hertz spin rate significant?

The 716 Hertz spin rate is significant because it exceeds the predicted theoretical limit of 350 rotations per second, challenging current models and suggesting that there may be an unknown factor at play in limiting neutron star spin.

How does gravitational radiation affect the spin of neutron stars?

Gravitational radiation causes neutron stars to lose energy over time. If a neutron star spins too fast, it emits gravitational waves, which can decelerate its spin rate. This process would slow down the star's rotation if it exceeds certain frequencies.

Why is there a question about whether 716 Hertz is the highest possible spin rate for neutron stars?

The question arises because two different neutron stars, observed at different times and locations, both spin at exactly 716 Hertz. This raises the possibility that 716 Hertz might represent an unofficial limit for neutron star spin rates.

What other neutron stars have similar spin rates to the 716 Hertz object?

Other neutron stars, like PSR G748 and PSR G952-0607, have been found to spin at similarly high rates, around 707 and 716 Hertz, respectively, suggesting that this may be the upper limit for neutron star spin.

What effect could the close orbit between the neutron star and white dwarf have on the system?

The close orbit between the neutron star and the white dwarf results in intense mass transfer from the white dwarf to the neutron star, which accelerates the neutron star’s spin and leads to the production of significant X-ray emissions and thermonuclear explosions.

What is the significance of the orbital period of the system in NGC 6624?

The orbital period of just 11 minutes is significant because it is the shortest known orbital period for any low-mass X-ray binary system, making this system an extreme example of close binary interactions.