Binary pulsar

Binary pulsars are one of the few objects which allow physicists to test general relativity because of the strong gravitational fields in their vicinities.

While Hulse was observing the newly discovered pulsar PSR B1913+16, he noticed that the rate at which it pulsed varied regularly.

It was concluded that the pulsar was orbiting another star very closely at a high velocity, and that the pulse period was varying due to the Doppler effect: As the pulsar was moving towards Earth, the pulses would be more frequent; and conversely, as it moved away from Earth fewer would be detected in a given time period.

The study of the PSR B1913+16 binary pulsar also led to the first accurate determination of neutron star masses, using relativistic timing effects.

This relativistic time delay is the difference between what one would expect to see if the pulsar were moving at a constant distance and speed around its companion in a circular orbit, and what is actually observed.

Prior to the first observation of gravitational waves in 2015 and the operation of Advanced LIGO,[3] binary pulsars were the only tools scientists had to detect evidence of gravitational waves; Einstein's theory of general relativity predicts that two neutron stars would emit gravitational waves as they orbit a common center of mass, which would carry away orbital energy and cause the two stars to draw closer together and shorten their orbital period.

[4][5] The measurements made of the orbital decay of the PSR B1913+16 system were a near perfect match to Einstein's equations.

Relativity predicts that over time a binary system's orbital energy will be converted to gravitational radiation.

Data collected by Taylor and Joel M. Weisberg and their colleagues of the orbital period of PSR B1913+16 supported this relativistic prediction; they reported in 1982[2] and subsequently[1][6] that there was a difference in the observed minimum separation of the two pulsars compared to that expected if the orbital separation had remained constant.

[7] The spin periods, magnetic field strengths, and orbital eccentricities of IMBPs are significantly larger than those of low mass binary pulsars (LMBPs).

The flow of matter from one stellar body to another often leads to the creation of an accretion disk about the recipient star.