A study of the glitch in the Vela Pulsar

The Vela Pulsar at the center of a nebula with the emission of a jet of particles (Image X-ray: NASA/CXC/Univ of Toronto/M.Durant et al; Optical: DSS/Davide De Martin)
The Vela Pulsar at the center of a nebula with the emission of a jet of particles (Image X-ray: NASA/CXC/Univ of Toronto/M.Durant et al; Optical: DSS/Davide De Martin)

An article published in the journal “Nature Astronomy” reports an analysis of an irregularity in the spin, a phenomenon called glitch in jargon, in the Vela Pulsar. A team of researchers led by Gregory Ashton of Monash University, Australia, analyzed the data collected by the Mount Pleasant Radio Observatory of the glitch detected on December 12, 2016. Probably this phenomenon is caused by internal interactions in the pulsar materials so studying it can provide information on the internal composition and on the processes taking place in an extreme object of this type.

Just over 950 light years from Earth, the Vela Pulsar is what remained after a supernova probably occurred between 11,000 and 12,000 years ago. This is the brightest pulsar at radio frequencies and on December 12, 2016 a glitch was detected with the Mount Pleasant Radio Observatory’s radio telescope. About 5% of pulsars showed glitches but in the Vela Pulsar this phenomenon happens about once every three years it’s become the object of specific studies that must be ready for the occasion given that a glitch lasts very little, in this case less than 13 seconds.

A new analysis of that glitch, in which the Vela Pulsar increased its spin to return to normal after a while, convinced the researchers that the inside of that neutron star is made of three different components. Dr. Paul Lasky, another researcher at Monash University and another of the authors of this research, explained that one of the components is a superfluid neutron soup in the crust’s inner layer that moves outwards and hits the external rigid crust making it spin. A second superfluid soup that moves into the core reaches the first one slowing it down. This is the first case in which that mechanism, which until now was only theoretical, was found in the observations.

Gregory Ashton mentioned another observation, which for now is without explanation. Just before the glitch, he and his colleagues noticed that the star seems to slow down its spin before resuming its speed. Perhaps it’s a phenomenon connected to the causes of the glitch but the researchers have no certainty and hope that this study will inspire new theories about neutron stars and glitches. They will keep on studying the Vela Pulsar during its regular spin to try to better understand its characteristics.

Surely there will be more studies of the Vela Pulsar, also for other phenomena such as the shrapnel ejected by the supernova that formed the nebula that surrounds it, objects for example of a study reported in an article published in the journal “Astronomy & Astrophysics” in August 2017. It’s a case in which observations of what happened after a star explosion can provide information on different phenomena.

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