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In a remarkable discovery, researchers from DTU Space have identified one of the universe's fastest-spinning neutron stars using an X-ray telescope stationed on the International Space Station (ISS). This small yet massive object, part of an "X-ray binary star system" called 4U 1820-30, lies in the Sagittarius constellation near the center of the Milky Way.
"We were studying thermonuclear by Robert Schreiber
Berlin, Germany (SPX) Oct 31, 2024
In a remarkable discovery, researchers from DTU Space have identified one of the universe's fastest-spinning neutron stars using an X-ray telescope stationed on the International Space Station (ISS). This small yet massive object, part of an "X-ray binary star system" called 4U 1820-30, lies in the Sagittarius constellation near the center of the Milky Way.
"We were studying thermonuclear explosions from this system and then found remarkable oscillations, suggesting a neutron star spinning around its center axis at an astounding 716 times per second," said DTU Space senior scientist Dr. Gaurava K. Jaisawal, part of the international research team behind the finding and the first author on an article published in the 'Astrophysical Journal'.
Dr. Jaisawal added, "If future observations confirm this, the 4U 1820-30 neutron star would be one of the fastest-spinning objects ever observed in the universe, matched only by another neutron star called PSR J1748 - 2446."
This neutron star was detected with NASA's NICER X-ray telescope, equipped with DTU Space-developed star tracker technology, which is mounted on the ISS. The tracker allows the X-ray instrument to continuously target distant, specific neutron stars within the Milky Way.
An Extreme Cosmic Phenomenon
Neutron stars, also known as "dead stars," are the remnants of massive stars that have exploded in supernovae. A few thousand are known to exist, each representing an extreme phenomenon in various ways. For instance, the neutron star in question is only 12 kilometers in diameter but has a mass 1.4 times that of the Sun.
This object is located 26,000 light years from Earth, a vast distance compared to the 4.3 light years between Earth and its nearest star, Proxima Centauri. Consequently, light from this neutron star has traveled 26,000 years to reach our planet.
Within this X-ray binary system, the neutron star is paired with a white dwarf companion of similar size to Earth. The white dwarf orbits the neutron star every 11 minutes, marking it as the shortest orbital period known in such systems.
Explosive Bursts of Energy
The neutron star's powerful gravitational field pulls material from the companion star. As enough material builds up on its surface, a violent thermonuclear burst occurs, releasing energy comparable to that of an atomic bomb.
"During these bursts, the neutron star becomes up to 100,000 times brighter than the Sun, releasing an immense amount of energy," explained DTU Space Associate Professor Jerome Chenevez, a contributor to the study published in 'Astrophysical Journal'. He continued, "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."
Through NICER observations conducted between 2017 and 2021, the research team detected 15 thermonuclear X-ray bursts from 4U 1820-30. One of these bursts revealed a unique signature, known as "thermonuclear burst oscillations," occurring at a frequency of 716 Hz. This frequency aligns with the neutron star's spin rate, confirming its remarkable rotation speed of 716 times per second.
Research Report:A Comprehensive Study of Thermonuclear X-Ray Bursts from 4U 1820 - 30 with NICER: Accretion Disk Interactions and a Candidate Burst Oscillation
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