GLITCH IN NEUTRON STAR REVEALS ITS HIDDEN SECRETS

OzGrav-Monash researchers Greg Ashton and Paul Lasky. Credit: Carl Knox, OzGrav

AS FEATURED IN THE AGE. 

Neutron stars are among the densest objects in the Universe, and they rotate extremely fast and regularly.
 
Until they don’t.
 
Occasionally, these neutron stars start to spin even faster, caused by portions of the inside of the star moving outwards. It’s called a ’glitch’, and it’s a rare glimpse into what lies within these mysterious objects.
 
In a recent paper published in Nature Astronomy, a team from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at Monash University; McGill University, in Canada; and the University of Tasmania, studied the Vela Pulsar: a neutron star in the southern sky, 1,000 light years away from Earth.
 
According to the paper’s first author Dr Greg Ashton, from OzGrav-Monash, only 5% of pulsars are known to glitch and Vela ‘glitches’ about once every three years. This makes Vela a famous prized jewel among ‘glitch hunters’ like Ashton and his colleague, Dr Paul Lasky, also from OzGrav-Monash.
 
By reanalysing data from observations of the Vela glitch in 2016, taken by co-author Jim Palfreyman from the University of Tasmania, Ashton and his team found that during the glitch the star started spinning even faster, before relaxing down to a final state. 
 
According to Dr Lasky, this observation (done at the Mount Pleasant Observatory in Tasmania) is particularly important because, for the first time, scientists got invaluable insights into the interior of the star, revealing that the inside of the star actually has three different components. 
 
“One of these components, a soup of superfluid neutrons in the core, moves outwards first and hits the rigid crust of the star causing it to spin up.  But then, a second soup of superfluid that moves in the crust catches up to the first causing the spin of the star to slow back down.  This overshoot has been predicted a couple of times in the literature, but this is the first real time it’s been identified in observations,” he said.
 
One such prediction of the overshoot came from the study’s co-author Vanessa Graber, from McGill University, who visited the Monash team as an OzGrav international visitor earlier this year. 
 
Another observation, according to Dr Ashton, defies explanation: “Immediately before the glitch, we noticed that the star seems to slow down its rotation rate before spinning back up.  We actually have no idea why this is, and it’s the first time it’s ever been seen!  We speculate it’s related to the cause of the glitch, but we’re honestly not sure,” he said. Ashton suspects this paper will spur some new theories on neutron stars and glitches