Russell Alan Hulse and Joseph Hooton Taylor Jr. discovered this binary pulsar at Arecibo in 1974; their January 1975 paper reports a roughly pulse period and orbital period. Its unseen companion was not detected as a second radio pulsar. Discovery of the orbit preceded the later binary-pulsar orbital decay test.[ref]
Discovery of a Pulsar in a Binary System by Russell Alan Hulse and Joseph Hooton Taylor Jr.. Discovery of a Pulsar in a Binary System, 15 January 1975, L51 opening and section II; L53 section IV
The 1993 Nobel Prize in Physics recognized the discovery.[ref]
All Nobel Prizes in Physics by Nobel Prize Outreach. 1993 entry, joint award and discovery motivation
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