PSR J0437−4715 is a pulsar. Discovered in the Parkes 70 cm survey,[5] it remains the closest and brightest millisecond pulsar (MSP) known. The pulsar rotates about its axis 173.7 times per second and therefore completes a rotation every 5.75 milliseconds. It emits a searchlight-like radio beam that sweeps past the Earth each time it rotates. Currently the most precisely located object outside of the Solar System, PSR J0437-4715 is 156.3 parsecs or 509.8 light-years distant.[3]
This pulsar is distinguished by being the most stable natural clock known and is debatably more stable than man-made atomic clocks.[6][7] Its stability is about one part in 1015. Two other pulsars, PSR B1855+09 and PSR B1937+21 are known to be comparable in stability to atomic clocks, or about 3 parts in 1014.
PSR J0437−4715 is the first MSP to have its X-ray emission detected and studied in detail.[8] It is also the first of only two pulsars to have the full three-dimensional orientation of its orbit determined.[9]
Optical observations indicate that the binary companion of PSR J0437-4715 is most likely a low-mass helium white dwarf.[2]
The pulsar is about 1.4 solar mass (M☉)[4] and the companion is about 0.25 M☉.[1] The pair revolve around each other every 5.75 days in nearly perfect circular orbits.[10]
^ abcVerbiest, J. P. W.; Bailes, M.; van Straten, W.; Hobbs, G. B.; et al. (2008). "Precision Timing of PSR J0437-4715: An Accurate Pulsar Distance, a High Pulsar Mass, and a Limit on the Variation of Newton's Gravitational Constant". The Astrophysical Journal. 679 (1): 675. arXiv:0801.2589. Bibcode:2008ApJ...679..675V. doi:10.1086/529576. S2CID5207918.
^ abDeller, A. T.; Verbiest, J. P. W.; Tingay, S. J.; Bailes, M. (2008). "Extremely High Precision VLBI Astrometry of PSR J0437-4715 and Implications for Theories of Gravity". The Astrophysical Journal. 685 (1): L67–L70. arXiv:0808.1594. Bibcode:2008ApJ...685L..67D. doi:10.1086/592401. S2CID8362572.
^Johnston, Simon; Lorimer, D. R.; Harrison, P. A.; Bailes, M.; Lynet, A. G.; Bell, J. F.; Kaspi, V. M.; Manchester, R. N.; et al. (1993). "Discovery of a very bright, nearby binary millisecond pulsar". Nature. 361 (6413): 613–615. Bibcode:1993Natur.361..613J. doi:10.1038/361613a0. S2CID4324763.