Researchers find a new way to weigh stars

London, Oct 6 (IANS) Researchers have developed a new method for measuring the mass of pulsars — highly magnetised rotating neutron stars formed from the remains of massive stars after they explode, says a new study.

“For pulsars, we have been able to use principles of nuclear physics, rather than gravity, to work out what their mass is — an exciting breakthrough which has the potential to revolutionise the way we make this kind of calculation,” said lead researcher Wynn Ho of University of Southampton’s mathematical sciences department.

Until now, scientists determined the mass of stars, planets and moons by studying their motion in relation to others nearby, using the gravitational pull between the two as the basis for their calculations.

“All previous precise measurements of pulsar masses have been made for stars that orbit another object, using the same techniques that were used to measure the mass of the Earth or Moon, or discover the first extrasolar planets. Our technique is very different and can be used for pulsars in isolation,” said study co-author Cristobal Espinoza of the Pontificia Universidad Catolica de Chile.

Pulsars emit a rotating beam of electromagnetic radiation, which can be detected by telescopes when the beam sweeps past the Earth, like observing the beam of a lighthouse. They are renowned for their incredibly stable rate of rotation, but young pulsars occasionally experience so-called ‘glitches’, where they are found to speed up for a very brief period of time.

The prevailing theory is that these glitches arise as a rapidly spinning superfluid within the star transfers its rotational energy to the star’s crust, the component that is tracked by observations.

Professor of applied mathematics at Southampton, Nils Andersson said: “Imagine the pulsar as a bowl of soup, with the bowl spinning at one speed and the soup spinning faster. Friction between the inside of the bowl and its contents, the soup, will cause the bowl to speed up. The more soup there is, the faster the bowl will be made to rotate.”

Wynn’s team included Andersson, Espinoza and Danai Antonopoulou of the University of Amsterdam.

They used new radio and X-ray data to develop a novel mathematical model that can be used to measure the mass of pulsars that glitch. The idea relies on a detailed understanding of superfluidity.

The team’s results have important implications for the next generation of radio telescopes being developed by large international collaborations, like the Square Kilometre Array (SKA) and the Low Frequency Array (LOFAR) of which Southampton is a British partner university.

“Our results provide an exciting new link between the study of distant astronomical objects and laboratory work in both high-energy and low-temperature physics. It is a great example of interdisciplinary science,” Andersson said.

A paper detailing the team’s work was published in the latest issue of journal Science Advances.

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