Scientists discover the slowest rotating radio neutron star ever recorded

Scientists have discovered a neutron star that is rotating at an unprecedentedly slow speed, slower than any of the more than 3,000 radio neutron stars measured to date. Neutron stars – the super-dense remnants of dead stars – usually spin at incredibly high speeds, taking just a few seconds, or even a fraction of a second, to complete a complete revolution on its axis. But a neutron star recently discovered by an international team of astronomers defies this rule, emitting radio signals at a relatively slow interval of 54 minutes. The team was led by Drs. Manisha Caleb of the University of Sydney and Emil Lenk of CSIRO, Australia’s national science agency, and includes scientists from the Universities of Manchester and Oxford. The results, published today in the journal Nature Astronomy, provide new insights into the complex life cycle of stars. Ben Stappers, professor of astrophysics at the University of Manchester, said: “We’re used to extreme experiments when studying radio-emitting neutron stars, but the discovery of a compact star that rotates very slowly yet emits radio waves was unexpected. This new generation of radio telescopes shows that expanding the boundaries of the search space can reveal surprises that will test our understanding.”

At the end of their lives, large stars run out of fuel and undergo a spectacular explosion called a supernova. What’s left is a stellar remnant called a neutron star, made up of trillions of neutrons packed into an extremely dense sphere with a mass 1.4 times that of the Sun, crammed into an area with a radius of just 10 km. Scientists have discovered an unexpected radio signal from a star that has traveled about 16,000 light years to Earth. The nature of the radio emission and the rate at which its rotation period changes suggest that it is a neutron star. However, researchers have not ruled out the possibility that it is an isolated white dwarf star with a very strong magnetic field. However, the absence of any other highly magnetic white dwarfs in the vicinity makes the neutron star explanation more plausible. Further research is needed to confirm which object this is, but both scenarios promise valuable insights into the physics of these extreme objects. The discovery could prompt scientists to rethink their decades-old understanding of neutron stars and white dwarfs; how they emit radio waves and what their populations look like in our Milky Way. Dr. Kaustubh Rajwade, an astronomer at the University of Oxford, said: “This discovery was based on the combination of the complementary capabilities of the ASKAP and MeerKAT telescopes, and our ability to simultaneously explore these objects on timescales of minutes and how they change their emission at the same time. The emission changes from second to second. Such a synergy can provide new insights into the evolution of these small objects.” The discovery was made using CSIRO’s ASKAP radio telescope in Wajari Yamatji Country, Western Australia. Because the radio telescope can cover a large portion of the sky at once, it can see things that researchers aren’t even looking for.

The research team was simultaneously monitoring gamma-ray sources and looking for fast radio bursts when they spotted the object slowly blinking in the data. Lead author Dr. Manisha Caleb from the University of Sydney’s School of Astronomy said, “What’s interesting is that this object has three different emission states, each with completely different properties. The MeerKAT radio telescope in South Africa played a key role in distinguishing between these states. If the signals had not come from the same point in the sky, we would not have believed that the same object was emitting these different signals.” The origin of such a long-period signal remains a deep mystery, with white dwarfs and neutron stars being the main suspects. But as further research continues, this discovery will further our understanding of one of the universe’s most enigmatic objects.

source/http://dx.doi.org/10.1038/s41550-024-02277-w