Abstract
Continued timing observations of the double pulsar PSR J0737–3039A/B, which consists of two active radio pulsars (A and B) that orbit each other with a period of 2.45 h in a mildly eccentric () binary system, have led to large improvements in the measurement of relativistic effects in this system. With a 16-yr data span, the results enable precision tests of theories of gravity for strongly self-gravitating bodies and also reveal new relativistic effects that have been expected but are now observed for the first time. These include effects of light propagation in strong gravitational fields which are currently not testable by any other method. In particular, we observe the effects of retardation and aberrational light bending that allow determination of the spin direction of the pulsar. In total, we detect seven post-Keplerian parameters in this system, more than for any other known binary pulsar. For some of these effects, the measurement precision is now so high that for the first time we have to take higher-order contributions into account. These include the contribution of the A pulsar’s effective mass loss (due to spin-down) to the observed orbital period decay, a relativistic deformation of the orbit, and the effects of the equation of state of superdense matter on the observed post-Keplerian parameters via relativistic spin-orbit coupling. We discuss the implications of our findings, including those for the moment of inertia of neutron stars, and present the currently most precise test of general relativity’s quadrupolar description of gravitational waves, validating the prediction of general relativity at a level of with 95% confidence. We demonstrate the utility of the double pulsar for tests of alternative theories of gravity by focusing on two specific examples and also discuss some implications of the observations for studies of the interstellar medium and models for the formation of the double pulsar system. Finally, we provide context to other types of related experiments and prospects for the future.
- Received 3 May 2021
- Accepted 25 October 2021
DOI:https://doi.org/10.1103/PhysRevX.11.041050
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by the Max Planck Society.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Viewpoint
ViewpointGeneral Relativity Withstands Double Pulsar’s Scrutiny
Published 13 December 2021
Sixteen years of timing data from the double pulsar confirm the validity of Einstein’s theory of general relativity to a new level.
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Popular Summary
Gravitational physics is currently described most accurately by Einstein’s general theory of relativity (GR). However, failed attempts to unify gravitation and quantum mechanics, describing nature on the largest and smallest scales, motivate the ongoing search for possible deviations from GR by rigorous testing with different experiments, from labs to astronomical observations. If deviations from GR exist, they may be detectable in strong gravitational fields of compact objects, such as neutron stars and black holes. Here, we study a system of two neutron stars orbiting each other every 147 minutes. By observing pulsed radio emission from the stars for more than 16 years, we detect many different relativistic effects and conduct tests of GR that are not accessible with other experiments.
We have followed rotations of the fast-spinning pulsar in the system, spanning about orbits and providing some of the most precise tests of GR so far, especially concerning the emission of gravitational waves and the propagation of photons in strong spacetime curvature. We develop new techniques and study previously unobservable effects such as the deflection of radio light in the gravitational field of a neutron star. We demonstrate how to use our observations to investigate the structural properties of neutron stars and discuss implications for the interstellar medium and the formation of binary neutron stars.
This work complements experiments with other techniques and serves as a blueprint on how to conduct similar studies with other systems in the future using new generations of telescopes.
