Scientists discover the slowest-spinning neutron star

Artist's depiction of CSIRO's ASKAP radio telescope with two versions of the mysterious celestial object: neutron star or white dwarf? Credit: Carl Knox/OzGrav.

Australian scientists from the University of Sydney and CSIRO have discovered a neutron star spinning more slowly than any other known neutron star.

This remarkable finding was published in Nature Astronomy.

Dr. Manisha Caleb from the University of Sydney Institute for Astronomy led the research.

She described the discovery as highly unusual, noting, “It is extraordinary to find a neutron star emitting radio pulses at such a slow rate.”

Most neutron stars, which are the remnants of large stars that exploded in supernovae, rotate extremely quickly, completing a full rotation in just seconds.

These stars are incredibly dense, packing 1.4 times the mass of our sun into a ball just 20 kilometers across. The extreme conditions of their formation typically result in rapid spinning.

However, this newly discovered neutron star, found using CSIRO’s ASKAP radio telescope in Western Australia, takes nearly an hour to complete one rotation. This is far slower than any other radio-emitting neutron star out of the more than 3,000 discovered so far.

The ASKAP radio telescope’s unique design allows it to observe a large part of the sky simultaneously, making it possible to spot unexpected phenomena. Dr. Emil Lenc, a CSIRO scientist and co-lead author on the paper, explained that the discovery was serendipitous. “We were monitoring a source of gamma rays and looking for a fast radio burst when I noticed this object slowly flashing in the data. ASKAP’s ability to scan wide areas of the sky made this possible.”

The slow rate of this neutron star’s radio emissions challenges existing theories about neutron star behavior and offers new insights into the life cycles of these stellar objects. The origin of such a slow signal is still a mystery, with two main types of stars being considered as possible sources: white dwarfs and neutron stars.

Dr. Caleb mentioned that the object shows three distinct emission states, each with different properties. The MeerKAT radio telescope in South Africa helped confirm that these signals came from the same object. “If the signals didn’t come from the same point in the sky, we would not have believed they were from the same object,” she said.

While an isolated white dwarf with a very strong magnetic field could potentially produce the observed signal, such stars have not been found nearby. On the other hand, a neutron star with extreme magnetic fields could explain the emissions more elegantly.

This discovery opens up new possibilities for studying neutron stars and understanding the complex behaviors of these fascinating cosmic objects.