Astronomy professors look to rare stars for answers on space-time warp

UBC astronomers were able to look at the space-time curvature warp inside a binary star before it slipped out of view.

Ingrid Stairs, professor of astronomy and astrophysics, studied the binary pulsar system J1906 along with a team of other researchers in the hopes of measuring the mass of the two neutron stars, which are the most dense and small stars in the universe, and the degree of the space-time curvature warp to determine how they interact with each other. J1906 is located 25,000 light years from Earth and will not come into view for observation for the next 160 years.

The research team also wanted to figure out the nature of the companion star, which serves as the centre of orbit for the two neutron stars.

“We were interested in measuring the masses of the two stars, in part hoping to figure out what the companion star is. The result is still a little ambiguous as the object could be either a white dwarf or another neutron star,” said Stairs.

White dwarf stars are very small, very dense stars that emit thermal energy and have low luminosity.

According to Stairs, the research team measured this binary pulsar system to clear up ambiguities about J1906, which is a largely unexplored area of our solar system, and determined the mass of astronomical objects within it.

The team found that the mass of the binary pulsar (a neutron star that rotates at high velocity and emits radiation) was 1.291 +/- 0.011 solar masses and the mass of the companion star to be 1.322 +/- 0.011 solar masses.

Astronomers usually use this unit of measurement to determine the mass of stars, but it can also extend to measurement of the mass of nebulae and galaxies.

Stairs also said that while the research team did not measure the spin axis or change in orientation of the stars, they did look at how their shapes changed based on the theory of general relativity. According to the research team's predictions, the pulsar disappeared from view after they were able to calculate the mass of the two stars.

“We didn't derive a measurement of the rate of precession of the neutron star's spin axis, but the profile shape changes and near-disappearance of the pulsar are qualitatively in agreement with the predictions of warped spacetime due to general relativity,” said Stairs.

In the future, Stairs hopes to use the knowledge gained about the pulsar star to get a clearer understanding of the types of stars that exist within J1906.

"In the medium term, we should be able to make a map of the radio emission beam of the pulsar, because we've been seeing different slices of that region as the spin axis precesses," said Stairs.