NASA delivers best-ever pulsar measurements and first surface map-with assistance from UAlberta scientists

UAlberta scientists part of team reaching a new frontier in understanding these super-dense neutron stars.

Andrew Lyle - 12 December 2019

Watch how NASA's Neutron star Interior Composition Explorer (NICER) has expanded our understanding of pulsars, the dense, spinning corpses of exploded stars. Pulsar J0030+0451, located 1,100 light-years away in the constellation Pisces, now has the most precise and reliable size measurement of any pulsar to date. The shapes and locations of its hot spots challenge textbook depictions of these incredible objects. Credit: NASA's Goddard Space Flight Center

Scientists have made the first precise measurements of a pulsar-the dense, whirling remains of an exploded star-thanks to NASA's Neutron star Interior Composition Explorer (NICER) X-ray telescope, in collaboration with University of Alberta scientists.

Sharon Morsink, associate professor in the Department of Physics, played a key role in the project, as part of the team that developed the theoretical framework and software used to translate the properties of the pulsar from the data collected by the NICER X-ray telescope.

"NICER is measuring the X-rays emanating from a pulsar roughly the size of Edmonton from a distance of 1,100 light-years," said Morsink. "The distances involved give us just a single pixel of data-which we need to then interpret into an understanding of the pulsar itself."

The pulsar, J0030+0451, is a neutron star that spins 205 times each second, with hot spots at the locations on its surface where there is a strong magnetic field.

"As it spins, we see the X-ray measurements get brighter and dimmer periodically as the hot spots rotate in and out of our view," explained Morsink. "With just one pixel, it is a difficult computational problem to use this data to get useful information about the star's properties."

But despite the challenge, scientists have done just that-providing the first precise measurement of both the mass and diameter of a neutron star, as well as some surprising findings.

"In particular, we found that the star is a sphere with a diameter that is just 26 km across, but weighs about one and a half times more than our sun," said Morsink. "We also found that the magnetic hot spots are all on one side of the star, suggesting a magnetic field similar to a horseshoe magnet-a totally unexpected result that, at the moment, we don't yet understand the reasons for. "

These new insights give scientists the first clear picture of the properties and surface of pulsars, yielding a better understanding of the universe around us.

UAlberta scientists part of team reaching a new frontier in understanding these super-dense neutron stars.

NICER is an X-ray telescope aboard the International Space Station. Credit: NASA

The research was published across several papers in The Astrophysical Journal Letters:

  • "Constraining the neutron star mass-radius relation and dense matter equation of state with nicer. ii. emission from hot spots on rapidly rotating neutron star" (doi: 10.3847/2041-8213/ab53eb)
  • "PSR J0030+0451 mass and radius from nicer data and the implications for the properties of neutron star matter" (doi: 10.3847/2041-8213/ab50c5)
  • "A NICER view of PSR J0030+0451: millisecond pulsar parameter estimation" (doi: 10.3847/2041-8213/ab481c)
  • "A NICER view of PSR J0030+0451: implications for the dense matter equation of state" (10.3847/2041-8213/ab451a)