Astronomers Discover the Fastest-Spinning Star in the Universe, Rotating 716 Times per Second

According to the Science Service of SaedNews, citing FaraDide, a team led by astrophysicist Gaurava Jaiswal of the Technical University of Denmark says this discovery confirms the current theoretical upper limit on neutron star rotation—believed to be around 730 rotations per second. Jaiswal explained, “We were studying thermonuclear bursts from this system when we noticed significant oscillations.”

“If future observations confirm this, neutron star 4U 1820-30 will rank among the fastest-spinning objects ever seen in the universe.”

Neutron stars represent one of the final stages in the evolution of massive stars.

When stars with masses 8 to 30 times that of the Sun exhaust their nuclear fuel, their cores can collapse while the outer layers are ejected in a supernova explosion. Without the outward pressure from nuclear fusion to support it, the core succumbs to gravity, forming a neutron star—a dense object with 1.1 to 2.3 times the Sun’s mass compressed into a sphere about 20 kilometers across. The matter inside these stars can behave in bizarre and extreme ways.

Astronomers have several ways of categorizing neutron star behavior. A magnetar is a neutron star with an extremely strong magnetic field. A pulsar is a neutron star spinning at incredible speeds, emitting beams of radio waves from its poles that sweep across space like a cosmic lighthouse.

Astronomers have known about 4U 1820-30 since at least the 1980s. It resides in the constellation Sagittarius as part of a tight binary system, composed of a neutron star and a white dwarf orbiting each other every 11.4 minutes.

As mass accumulates on the neutron star, it becomes denser and hotter until it erupts in thermonuclear bursts—stellar sneezes, essentially. Jaiswal and colleagues studied these explosions using NASA’s Neutron star Interior Composition Explorer (NICER).

Jerome Chenevez, an astrophysicist at the Technical University of Denmark, says, “During these bursts, the neutron star can shine up to 100,000 times brighter than the Sun, releasing tremendous amounts of energy.”

“These are extreme events. By studying them, we gain new insights into the life cycles of binary star systems and the formation of elements in the cosmos.”

Between 2017 and 2022, the team recorded 15 of these thermonuclear bursts. While analyzing the data, they found something remarkable: one burst showed a peculiar oscillation at 716 hertz. The signal suggested the star was spinning rapidly during the explosion—a conclusion the researchers say is likely correct.

This could mean that neutron star 4U 1820-30 is an X-ray pulsar rotating 716 times per second, powered by thermonuclear bursts. Since PSR J1748-2446ad is a radio pulsar, 4U 1820-30 may now be the fastest-known nuclear-powered pulsar.

Further observations are needed to confirm this finding. If verified, the discovery will provide a powerful new tool for studying neutron stars and the extreme rotational speeds they can reach before tearing themselves apart.