Microscopic deformation the size of a bacterium from a neutron star deduced 4,500 light years away

Imagine that the size of a bacterium is measured at a distance of about 4500 light years. That would be an incredible measure, given that a bacterium is so small that a microscope is needed to see it, and how far light can travel in 4,500 years, given that it can circle the Earth longer. seven times in just one second. . But a small deformation the size of a bacterium, which is an additional height of a few micrometers in one direction, has now been deduced for a neutron star at a distance of about 4,500 light years, according to research by Professor Sudip Bhattacharyya of the Tata Institute of Fundamental Research (TIFR), India. This research is published in a new article in Monthly notices from the Royal Astronomical Society.

A microscopic deformation of the neutron star in the binary star system PSR J1023 + 0038 is deduced. Here, the axis of rotation of the star is perpendicular to the plane of the figure. The extra height of the neutron star in one direction is only a few micrometers, the size of a bacterium, estimated at a distance of about 4,500 light years. Credit: Sudip Bhattacharyya

Neutron stars are incredibly dense cosmic objects. They’re about the size of a city, but contain more matter than in the Sun, and a handful of stellar stuff would trump a mountain on Earth. We observe that some of them rotate several hundred times in a second, and we call them millisecond pulsars. A slight asymmetry or deformation around the axis of rotation of such a star would cause the emission of gravitational waves continuously.

Gravitational waves, which are ripples in space-time, have recently opened a new window into the universe. But so far they have been found as transient fusion phenomena of black holes and neutron stars. Continuous gravitational waves, for example from a slightly distorted and spinning neutron star, have so far not been detected. Current instruments may not have the ability to detect these waves if the strain is too low.

However, one way to indirectly infer such waves and measure this strain is to estimate the contribution of the waves to the downward rotational speed of the pulsar, which was not possible until now. The PSR J1023 + 0038 is a unique cosmic source for this purpose, as it is the only millisecond pulsar for which two spin-down speeds, in the mass transfer phase of the companion star and in the phase where it does not there is no mass transfer, were measured. Using these values, and primarily a fundamental principle of physics, namely the conservation of angular momentum, Bhattacharyya deduced continuous gravitational waves and estimated the microscopic deformation of the neutron star.

Reference: “The permanent ellipticity of the neutron star in the PSR J1023 + 0038” by Sudip Bhattacharyya, August 18, 2020, Monthly notices from the Royal Astronomical Society.
DOI: 10.1093 / mnras / staa2304