Using a telescope on the International Space Station, researchers have discovered a neutron star in the Milky Way that rotates at an incredible 716 times per second - among the fastest ever discovered
The Milky Way still holds mysteries related to the universe, and researchers from DTU have discovered a new mystery. Using an X-ray telescope on the International Space Station, they observed a very dense, rapidly rotating neutron star. The star, named 4U 1820-30, is part of an X-ray emitting binary star system located in the Sagittarius group near the center of our galaxy.
"We studied thermonuclear explosions from this system and then found unusual oscillations, indicating a neutron star spinning around its central axis at an incredible 716 times per second," explains DTU's Dr. Gurva Jaiswal, lead author of the paper.
"If future observations confirm this, the neutron star 4U 1820-30 will be one of the fastest rotating objects observed in the universe, matched only by another neutron star called PSR J1748–2446."
The team made this discovery using NASA's NICER X-ray telescope, which is equipped with star tracker technology developed at DTU. The star tracker system mounted on the outside of the space station keeps the telescope pointed precisely at distant neutron stars throughout the Milky Way.
A neutron star, also known as a dead star, is the remnant of a large massive star that exploded in a supernova. Several thousand of them have been discovered, and they are extreme in many ways.
They are the densest objects that can be observed in the cosmos. This neutron star is only 12 km in diameter but its mass is 1.4 times that of the Sun.
It is located 26,000 light years from Earth. for comparison. The distance to the nearest star to Earth, Proxima Centauri, is about 4.3 light years. This means that light from Proxima Centauri takes 4.3 years to reach us, while light from the neutron star travels 26,000 years before we can observe it here.
The neutron star is part of a binary star system that emits X-rays. Such a system includes two stars orbiting each other. What's also unique about the 4U 1820-30 system is that the companion star is a white dwarf about the size of Earth. It orbits the neutron star every 11 minutes, and this is the system with the shortest orbit cycle known.
Because of its strong gravity, the neutron star pulls material from the companion star. When enough material accumulates on the surface of the neutron star, a powerful thermonuclear explosion occurs, similar to an atomic bomb.
"During these explosions, the neutron star becomes up to 100,000 times brighter than the Sun, releasing an enormous amount of energy," explains Jérôme Schnabe of DTU, one of the authors of the paper.
"So these are very extreme events, and from their detailed study we get new insights into the exciting life cycles of binary star systems and the formation of elements in the universe."
The researchers discovered 15 X-ray-emitting thermonuclear explosions from the X-ray binary star system 4U 1820-30. One of the explosions showed a signature called "thermonuclear explosion oscillations," which occur at a frequency of 716 Hz, which matches the rotation frequency of the neutron star itself, meaning it spins on its axis at a record rate of 716 times per second.
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