Binary pulsar

A binary star system containing a pulsar, a rapidly rotating neutron star whose regular radio pulses reveal the stars’ orbital motion. Precise timing can test theories of gravity.

Pulsar timing: The measurement of a pulsar’s rotation through the arrival times of its pulses. Timing variations reveal the binary orbit and changes in pulse arrival caused by gravity.
Hulse–Taylor binary: The binary pulsar PSR B1913+16, discovered by Russell Hulse and Joseph Taylor in 1974. Its shrinking orbit provided the first indirect evidence for gravitational-wave emission.
Russell Hulse: An American astrophysicist who discovered the binary pulsar PSR B1913+16. His discovery supplied the first system used to measure relativistic orbital decay.
General relativity: Einstein’s theory describing gravity as the curvature of spacetime by matter and energy. Binary-pulsar measurements test its predictions in strong gravitational fields.
Pulsar–white dwarf binary: A binary system containing a pulsar and a white dwarf companion. Its asymmetric components enable tests unavailable in binaries with two neutron stars.
Keplerian orbit: An orbit governed by Newtonian gravity, described by parameters such as period and eccentricity. Its orbital parameters provide the baseline against which relativistic deviations are measured.
Double pulsar: The system PSR J0737−3039, in which both neutron stars are observed as pulsars. Both stars can be timed, enabling unusually precise tests of relativistic gravity.
Joseph Taylor: An American astrophysicist who studied PSR B1913+16 and its changing orbit. His timing measurements established the system’s agreement with gravitational-wave energy loss.
Gravitational waves: Ripples in spacetime that propagate outward from accelerating masses. Orbital decay in certain binaries matches energy loss predicted from their emission.
Double neutron star system: A binary star system in which both stars are neutron stars. It contrasts with pulsar–white dwarf systems, though one or both neutron stars may be pulsars.

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