Astrophysicists have discovered one of the fastest-spinning neutron stars in the universe.

One of the densest objects in the universe, neutron stars are remnants of massive stars that have exploded as supernovae. These objects have a mass more than 1.4 times that of the Sun and a diameter of approximately 20 to 25 kilometers. Recently, an international research team discovered one of the fastest-spinning neutron stars in the universe using the NICER X-ray telescope, which is mounted on the International Space Station.

2024-10-31 10:01:04https://naked-science.ru/article/astronomy/nejtronnaya-zvezda

The ultra-compact binary system 4U 1820–30, located 27,400 light-years away from our planet in the globular cluster NGC 6624 in the constellation Sagittarius, consists of a neutron star and its companion — likely an Earth-sized white dwarf. The period of its rotation around the common center of mass of the two stars is a record-breaking 11.4 minutes.

In a study whose results are presented in the journal The Astrophysical Journal, scientists from the National Space Institute of Denmark (DTU Space), in collaboration with colleagues from other countries, described 15 thermonuclear bursts observed in the X-ray range in the 4U 1820–30 system from 2017 to 2022 using NASA's NICER instrument.

During the analysis of one of the bursts, the team detected oscillations at a frequency of 716 hertz and suggested they were observing a neutron star rotating 716 times per second around its axis. Due to its powerful gravity, the object absorbs material from its companion — the white dwarf. It is worth noting that when a sufficient amount of material accumulates on the surface of the neutron star, it becomes 100,000 times brighter than the Sun and releases a colossal amount of energy as a result of a powerful thermonuclear explosion.

The authors of the new study indicated that if further observations confirm their findings, the object 4U 1820–30 would share the title of the fastest-spinning neutron star with PSR J1748–2446ad, located in the Terzan 5 globular cluster, which also rotates 716 times per second around its axis.

Notably, all recorded bursts exhibited an expansion of the neutron star's atmosphere, which occurs when its surface rapidly expands due to a powerful energy release and then returns to its original state. The radius of expansion during one of the bursts reached 902 kilometers.

The results also showed that the bursts alter the ionization of the accretion disk — a structure of matter swirling around the neutron star and gradually falling onto it. According to astrophysicists, this indicates a complex interaction between the bursts and the accreting material.

Thus, the team has identified a candidate for one of the fastest-spinning neutron stars. This discovery approaches the theoretical limit of neutron star rotation speed (estimated to be around 730 hertz) and could significantly expand our understanding of fundamental physical laws in the universe.

Astrophysicists plan to continue observing 4U 1820–30 to confirm the detected oscillations and study the mechanisms leading to such extreme phenomena. Further research will provide valuable insights into the properties of super-dense matter in neutron star cores and enhance our understanding of the processes that limit their rotation speed.