Neutron stars are invisible to the naked eye, but measuring their masses and radii could eventually yield startling insights about nuclear energy.
Sudip Bhattacharyya, a scientist at the Tata Institute of Fundamental Research’s department of astronomy and astrophysics, and two foreign collaborators, have discovered a trend in explosions on these stars’ surfaces that is likely to help in measuring their radii.
“In a double star system, when hydrogen and helium from a companion star pile up on the neutron star’s surface, it bursts like a hydrogen bomb,” explained Bhattacharyya, 36, whose research has been accepted by the Monthly Notices of the Royal
Astronomical Society, a peer-reviewed journal. “We have used these bursts as a tool to measure the neutron stars.”
Bhattacharyya collaborated with Coleman Miller, professor of astronomy at the University of Maryland in the US, and Galloway Monash of the University of Australia.
For the past year, Bhattacharyya analysed 43 neutron stars and 900 bursts through the Rossi X-Ray Timing Explorer installed on a NASA satellite that collated data over the last 13 years.
Neutron stars, which are the dense remnants of exploded stars and are eight times more massive than the sun, can be seen only above the earth’s atmosphere, through X-rays and radio waves.
Their cores are the only known places in the universe containing matter at several times nuclear density, explained Miller, in an e-mail interview.
Scientists already have a good idea of how matter behaves at nuclear densities, namely when the number of neutrons and protons in the nucleus are roughly equal. They hope that by studying neutron stars, they will better understand how denser nuclear matter behaves, he explained.
Yet since one cannot study this matter directly, astrophysicists strive to study these stars’ macroscopic properties, from which they hope to make key inferences about the dense cores.
One such property is the radius of the star. Scientists hope to estimate the radius by studying thermonuclear bursts on the star’s surface.
“If one needs to study basic matter, then the study of neutron stars is important,” said Bhattacharyya.