A new method for measuring the mass of pulsars has been developed by researchers from the University of Southampton (UK), and it could lead to major changes in today’s telescopic technologies.
Pulsars are highly magnetized, rotating neutron stars that are formed from the remains of massive stars after they’ve exploded into supernovae. Up to this point, the mass of stars, along with moons and planets, was determined by studying their motion in relation to others nearby, which was determined by using the gravitational pull between the two as the basis for all calculations.
The method proved effective for most cases; however, not so much with young pulsars. The new method developed by the Southampton researchers now allows scientists to accurately measure their mass, even if a star exists on its own in space.
“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 revolutionize the way we make this kind of calculation,” explained lead researcher Dr. Wynn Ho, of the University’s Mathematical Sciences department.
Collaborator Dr. Cristobal Espinoza of the Pontificia Universidad Catolica de Chile, adds: “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.”
Pulsars emit a rotating beam of electromagnetic radiation, which is picked up by telescopes whenever the beam passes over Earth. While these beams are largely known for their stable rate of radiation, young pulsars sometimes experience ‘glitches’; that is, they randomly speed up for a short period of time.
These glitches occur due to the rapidly spinning superfluid within the star transferring its rotational energy to the star’s crust. “Imagine the pulsar as a bowl of soup, with the bowl spinning at one speed and the soup spinning faster, explains Nils Andersson, 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.”
By using new radio and x-ray data, the team of researchers was able to develop their new mathematical model for measuring the mass of pulsars that ‘glitch’. In short, their breakthrough is based on superfluidity — that 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. Combining observational information collected via earth-based telescopic technologies with the aforementioned laws of nuclear physics, one can better determine the mass of the star.
The results of the Southampton team’s efforts will have major implications for the next generation of radio telescopes being developed by large international collaborations, including the Square Kilometer Array and Low Frequency Array. The goal is to update the technologies so that researchers can better monitor and measure future discovered pulsars.
“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,” said Professor Andersson. “It is a great example of interdisciplinary science.”
Read the full report, entitled “Pinning down the superfluid and measuring masses using pulsar glitches,” which was published in Science Advances.
Via the University of Southampton
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