A new method of measuring the mass of pulsars developed by scientists from the University of Southampton allows researchers to determine the mass of these highly magnetized neutron stars formed following supernovae, even if the object exists alone in outer space.
Typically, the mass of a pulsar (or any star, planet or moon) is determined by studying its motion in relation to other nearby objects, based on the gravitational pull between the entities, Dr. Wynn Ho and his colleagues explained. However, as the authors reported in Scientific Advances, their new method does not require the presence of a second object.
“For pulsars, we have been able to use principles of nuclear physics, rather than gravity, to work out what their mass is,” Dr. Ho said, calling their discovery “an exciting breakthrough which has the potential to revolutionize the way we make this kind of calculation.”
“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,” added Dr. Cristobal Espinoza of the Pontificia Universidad Catolica de Chile. “Our technique is very different and can be used for pulsars in isolation.”
Superfluid-caused glitches used to calculate star weight
Pulsars, the study authors explained, emit a rotating bean of electromagnetic radiation that tends to be extremely stable. However, sometimes these beams experience “glitches” that causes them to speed up for brief periods of time. This is likely due to rotational energy transfer from quick-spinning superfluid within the star to the star crust that can be tracked using telescopes.
In their paper, they explained that the examined a model to test a variety of different superfluid-based glitch models against recently collected data from actual pulsar glitch events. They found that one model sufficiently explained up to 45 years worth of observational data, then developed a new technique to measure pulsar masses using a combination of radio and x-ray data.
The magnitude and frequency of the pulsar glitches depend on the amount of superfluid in the star, as well as the mobility of the superfluid vortices within, Dr. Ho’s team explained. Using a combination of observational data combined with the principles of nuclear physics, they were able to device a way to determine the star’s mass—a discovery which they believe could have a profound impact on the development of next-generation radio telescopes.
“Imagine the pulsar as a bowl of soup, with the bowl spinning at one speed and the soup spinning faster,” said research team member Nils Andersson, a professor of applied mathematics at Southampton. “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.”
“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.” the professor added. “It is a great example of interdisciplinary science.”
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Feature Image: University of Southampton
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