doi:10.1038/nindia.2014.130 Published online 26 September 2014
By analysing observational data using analytical models, researchers have gained new insights into how strong gravitational fields drag space–time inside distant fast-rotating neutron stars1. These insights will be useful for understanding how gravity affects the magnetic field distribution of neutron stars.
The general theory of relativity predicts that massive rotating neutron stars will drag space–time around themselves. This phenomenon is known as the frame-dragging effect. Previous studies had measured the values of the frame-dragging effect for slowly rotating neutron stars, but those values are not useful for understanding the frame-dragging effect in rapidly rotating neutron stars.
To obtain insights into the frame-dragging effect in rapidly rotating neutron stars, the researchers calculated the values of the frame-dragging effect for three distant fast-rotating neutron stars by developing analytical models to analyse observational data.
The researchers found that the frame-dragging value peaked at the centre of the stars and that the value decreased near the equator and poles on the star surfaces. The rotational speed of the star does not influence these values. The researchers performed detailed theoretical calculations and found that the values of the frame-dragging effect tend to be negligible inside neutron stars even in the presence of a very strong gravitational field.
This is very eccentric behaviour of the frame-dragging effect. Previous studies predicted that the values of the frame-dragging effect varied inversely with distance for massive rotating celestial bodies such as neutron stars, but the findings of this study refute that idea. The researchers say that their results provide exact values for the frame-dragging effect both inside and outside rotating neutron stars, including at their centres.