Scientists have discovered a new method that allows them to weigh the mass of pulsars without needing to look at other nearby objects.
Pulsars are magnetized rotating neutron stars that are born from the remains of massive stars that have exploded as supernovae. Until now, scientists measured the mass of these objects by looking at their rotation in relation to nearby planets and moons that impose gravitational pulls, the University of Southampton reported. This new method of measurement will allow researchers to estimate a pulsar's mass even if it is isolated 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," said Wynn Ho, of Mathematical Sciences at the University of Southampton.
Pulsars emit a rotating beam of electromagnetic radiation that can be spotted by Earth-bound telescopes. The rotation of these pulsars is generally regular, but some younger one can experience "glitches" in which they temporarily speed up. Researchers believe these glitches are caused by a "rapidly spinning superfluid" within the star that transfers rotational energy to the crust.
"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," explained Nils Andersson, professor of Applied Mathematics at Southampton.
In this new measurement technique, the scientists used new radio and X-ray data to develop a mathematical model that can measure the mass of glitchy pulsars. The mass of the star can be determined through a combination of observational information and principles of nuclear physics that focus on the quantity and mobility of superfluid vortices within.
The findings could have applications for the development of the next generation of large radio telescopes, such as the Square Kilometre Array (SKA) and the Low Frequency Array (LOFAR).
"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 concluded.
The findings were published in a recent edition of the journal Science Advances.
