The nearest millisecond pulsar, PSR J0437-4715, located about 510 light-years from Earth in the southern constellation of the Painter, has a radius of 11.4 kilometers and a mass of 1.4 times the mass of the Sun.

These precise measurements were carried out by a research team led by the University of Amsterdam (Netherlands) and revealed new details about the composition and magnetic field of this neutron star. The results of the research were published in a series of scientific papers.

PSR J0437 is a pulsar orbiting a neutron star that emits electromagnetic radiation. It spins on its axis 174 times per second and has a companion – a white dwarf. Like a beacon, the pulsar sends radio waves and X-rays to Earth every 5.75 milliseconds, making it the closest and brightest pulsar by millisecond and a more stable “clock” than an artificial atomic clock.

For their study, the scientists used data from the NICER X-ray telescope on the ISS and modeling of electromagnetic pulses. They calculated complex statistical models that give the star’s radius using mass measurements made on the Dutch national supercomputer Snellius by Daniel Reardon (Swinburne University of Technology, Australia) and colleagues at the Parkes Pulsar Timing Array. The researchers also mapped the temperature distribution of the magnetic poles.

Lead researcher Devarshi Choudhury (University of Amsterdam, Netherlands) expressed her delight with the measurement results: “We previously hoped to be able to calculate the radius precisely. And it would be great if we could show that the hot magnetic poles on the star’s surface are not exactly opposite each other. We have managed to do both.”

The new measurements point to a “softer equation of state” than previously thought, meaning that the maximum mass of neutron stars should be lower than some theories predict. This finding is consistent with observations of gravitational waves, as co-author and neutron star expert Hanna Watts (University of Amsterdam) points out.