NEW RESEARCH in the Milky Way galaxy reveals the existence of neutron stars rotating on their axis at very high speeds. This star rotates 716 times per second, making it one of the fastest rotating objects ever observed.
The Milky Way Galaxy still holds many secrets about the universe. Now, researchers from DTU have succeeded in uncovering one of these secrets using the X-ray space telescope installed on the International Space Station (ISS). This object is a small but very massive and rapidly rotating neutron star, part of an X-ray binary star system called ‘4U 1820-30’. This star is located in the constellation Sagittarius, towards the center of our galaxy.
“We were studying the thermonuclear explosion of this system and then discovered extraordinary oscillations, which indicated the presence of a neutron star rotating around its axis at an incredible speed of 716 times per second,” said Dr. Gaurava K. Jaisawal, senior scientist at DTU Space, is part of the international research team behind the new discovery and lead author of an article about it just published in the Astrophysical Journal.
“If future observations confirm this, the neutron star 4U 1820-30 will be one of the fastest rotating objects ever observed in the universe, comparable only to another neutron star called PSR J1748-2446.”
This neutron star was observed using NASA’s NICER X-ray telescope, which is equipped with star tracking technology from DTU Space and installed outside the International Space Station. The star tracking camera system ensures that the X-ray instrument is always pointed in the right direction and precisely targets small, distant neutron stars in the Milky Way galaxy.
Extreme phenomena are very far from here
Neutron stars, also called dead stars, consist of the remains of large, massive stars that have exploded in supernovae. Several thousand neutron stars have been discovered, and they are extreme in many ways.
They are the densest observable objects in the cosmos. This neutron star is only 12 km wide but has a mass 1.4 times greater than the Sun.
This star is located 26,000 light years from Earth. For comparison, the distance to Earth’s nearest star, Proxima Centauri, is about 4.3 light years. This means that light from Proxima Centauri took 4.3 years to reach us on Earth, while light from this neutron star took 26,000 years before we could observe it on Earth.
This neutron star is part of an X-ray binary star system. Such a system consists of two stars orbiting each other. What is also unique about the ‘4U 1820-30’ system is that its companion star is a white dwarf which is almost the same size as Earth. This star is known to orbit a neutron star every 11 minutes, making it the system with the shortest known orbital period.
The surface eruption was as powerful as an atomic bomb
Due to its very strong gravity, this neutron star attracts material from its companion star. When enough matter accumulates on its surface, a violent thermonuclear eruption occurs on the neutron star, similar to an atomic bomb.
“During these eruptions, the neutron star becomes up to 100,000 times brighter than the Sun, releasing enormous amounts of energy,” explains Associate Professor at DTU Space, Jerome Chenevez, who contributed to the new article in the Astrophysical Journal.
“So, we are dealing with very extreme events, and by studying them in detail, we gain new insights into the life cycles of binary star systems and the formation of elements in the universe.”
Through observations made with NICER between 2017 and 2021, researchers discovered 15 thermonuclear X-ray eruptions from an X-ray binary star system called ‘4U 1820-30’. One of these eruptions showed a signature known as a ‘thermonuclear eruption oscillation’, which occurred at a frequency of 716 Hz.
These eruptive oscillations correspond to the rotation frequency of the neutron star itself, meaning that it rotates on its axis at a record high rate of 716 times per second. (Science Daily/Z-3)
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**Interview with Dr. Gaurava K. Jaisawal on the Discovery of the Fastest Neutron Star**
**Editor:** Welcome, Dr. Jaisawal! Thank you for joining us today. Your team recently made a remarkable discovery of a neutron star rotating at an incredible speed of 716 times per second. Can you tell us more about how this discovery came about?
**Dr. Jaisawal:** Thank you for having me! We were initially investigating a thermonuclear explosion within the X-ray binary star system known as 4U 1820-30. During our observations using NASA’s NICER X-ray telescope, we detected extraordinary oscillations in the X-ray emission that indicated the presence of this incredibly fast neutron star. It was quite an exciting moment for our team!
**Editor:** That’s fascinating! What exactly makes this neutron star so unique compared to others that have been observed?
**Dr. Jaisawal:** This neutron star stands out because of its rapid rotation speed. At 716 times per second, it is among the fastest rotating objects known in the universe. Additionally, neutron stars are incredibly dense; this one is only 12 kilometers wide but has a mass about 1.4 times that of our Sun. The extreme conditions and speed make it a remarkable subject for study.
**Editor:** You mentioned that the neutron star is located in the Milky Way, specifically in the constellation Sagittarius. How far is it from Earth?
**Dr. Jaisawal:** It is approximately 26,000 light years away from us. To put that into perspective, light from this neutron star took 26,000 years to reach us, while the nearest star, Proxima Centauri, is only about 4.3 light years away.
**Editor:** That’s an enormous distance! Can you explain the significance of using the NICER X-ray telescope for this research?
**Dr. Jaisawal:** Absolutely. NICER, or the Neutron star Interior Composition Explorer, is specifically designed to observe X-ray emissions from neutron stars. Its advanced star tracking technology allows us to precisely focus on small and distant objects in the universe. This capability has been crucial in our detection of the rapid rotation and unique properties of the 4U 1820-30 neutron star.
**Editor:** With this discovery, do you think we could learn more about the nature of neutron stars and the phenomena surrounding them?
**Dr. Jaisawal:** Definitely! Each neutron star presents an opportunity to gain insights into extreme physics, gravitational effects, and the behavior of matter under intense pressure. As we continue our observations and gather more data, we hope to piece together more about the lifecycle and characteristics of these fascinating celestial bodies.
**Editor:** Thank you, Dr. Jaisawal, for sharing your insights with us today. This discovery is not just important for science, but it also opens up new avenues for understanding the universe.
**Dr. Jaisawal:** Thank you for having me! I’m excited about what we’ll discover next.
