Top Spin: Neutron star found to be rotating at an astonishing 716 times per second

Researchers have discovered that the neutron star in the binary system 4U 1820-30 rotates at an astonishing speed of 716 times per second, making it one of the fastest-spinning objects ever observed in the universe. The discovery was made by a research team led by astrophysicist Gaurava K. Jaisawal from the Technical University of Denmark, with results published in The Astrophysical Journal. During their study of thermonuclear bursts from this system, they discovered extraordinary oscillations indicating the neutron star's rapid rotation.

"While we were studying thermonuclear bursts from this system, we discovered extraordinary oscillations indicating a neutron star rotating around its axis at an amazing speed of 716 times per second," Jaisawal, a senior scientist at DTU Space, said. According to the researcrher If the collected data is confirmed, the neutron star 4U 1820-30 will become one of the fastest rotating objects ever observed in the entire Universe, matched only by another neutron star called PSR J1748-2446.

The phenomenon was discovered thanks to NASA's Neutron Star Interior Composition Explorer (NICER), mounted on the International Space Station, which recorded 15 explosions between 2017 and 2022. The researchers discovered 15 thermonuclear X-ray bursts from the X-ray binary star system 4U 1820-30 during this period. When analyzing the data from these explosions, they found an unusual oscillation with a frequency of 716 Hertz, suggesting that the neutron star in 4U 1820-30 could be an X-ray pulsar. More observations will be required to verify this finding. If confirmed, the results will provide a new tool for studying neutron stars and understanding how far they can go before self-destructing.

Astrophysicist Jerome Chenevez from the Technical University of Denmark stated, "During these explosions, the neutron star becomes up to 100,000 times more luminous than the Sun, releasing an immense amount of energy. So we are dealing with very extreme events, and by studying them, we obtain new information about the life cycles existing in binary star systems and about the formation of elements in the Universe." He adds, "So we are dealing with very extreme events, and by studying them in detail, we get new insights into the exciting life cycles of binary star systems and the formation of elements in the universe."

The neutron star 4U 1820-30 is located approximately 26,000 light-years away from Earth in the constellation Sagittarius, within the globular cluster NGC 6624. It has a mass 1.4 times greater than the mass of the Sun and is only 12 kilometers (about 7.5 miles) across. These extremely compact objects possess a mass ranging from 1.1 to 2.3 times that of the Sun but are compressed into a sphere only 20 kilometers in diameter.

4U 1820-30 is a binary system that includes a neutron star and a white dwarf approximately the same size as Earth, with a tight orbit that allows the neutron star to complete an orbit in just 11.4 minutes. The proximity of the two stars is such that the neutron star continuously siphons material from its white dwarf companion, allowing it to cannibalize its companion and strip it of material. This material accumulates on the neutron star's surface, becoming denser and hotter until it reaches critical mass and detonates in a violent thermonuclear explosion, similar to an atomic bomb, releasing an incredible amount of energy.

Neutron stars represent one of the final evolutionary stages of a massive star, forming when stars with at least eight times the mass of the Sun run out of fuel for nuclear fusion. A star with a mass between eight and 30 times that of the Sun, after exhausting the fuel in its core, undergoes a collapse that can lead to a violent supernova explosion, expelling the outer material, while the core collapses under gravity, giving rise to the neutron star.

Neutron stars are extreme in many ways and are the densest objects ever observed in the cosmos, being the remnants of massive stars after they explode in a supernova. Matter inside neutron stars can behave in unusual ways, and it is difficult to find words to describe their density: the matter that composes them can become truly strange, as can their behaviors. A pulsar is a neutron star that rotates at dizzying speeds, emitting beams of radio waves from its poles, and these beams propagate into space, making it appear as a cosmic lighthouse that pulses constantly. Neutron stars are known to rotate quickly, with some rotating hundreds of times per second.

NASA's NICER (Neutron star Interior Composition Explorer) features star tracker technology that ensures accurate targeting of distant neutron stars. The data collected by NICER was crucial in identifying the rapid rotation of the neutron star in 4U 1820-30. Eventually, the amassing material triggers thermonuclear blasts that can forge heavy elements such as gold and platinum. By studying these extreme events in detail, researchers gain new insights into the exciting life cycles of binary star systems and the formation of elements in the universe.

The 4U 1820-30 binary star system has the shortest orbital period ever seen and has been known to exist since at least the 1980s. The neutron star and its white dwarf companion have a volatile relationship, with the white dwarf completing an orbit around the neutron star every 11 minutes, making it the system with the shortest known orbital period of 685 seconds. This discovery opens new possibilities for studying the evolution of neutron stars. If confirmed, it would provide a new tool for understanding how far neutron stars can go before self-destructing.

Sources: Science Alert, Scienze Notizie, Spektrum der Wissenschaft, Mashable

This article was written in collaboration with generative AI company Alchemiq