Joseph H. Taylor Jr. is an American astrophysicist. He was awarded Nobel Prize in Physics with Russell A. Hulse "for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation" in 1993.
In 1974, using the large radio telescope at Arecibo, Puerto Rico, Taylor and Hulse discovered a pulsar (a rapidly spinning neutron star) emitting radio pulses at intervals that varied in a regular pattern, decreasing and increasing over an eight-hour period. They concluded from these signals that the pulsar must be alternately moving toward and away from the Earth—i.e., that it must be orbiting around a companion star, which the two men deduced was also a neutron star. Their discovery of the first binary pulsar, PSR 1913 + 16, provided an unprecedented test of Albert Einstein’s theory of gravitation, which, according to the general theory of relativity, predicts that objects accelerated in a strong gravitational field will emit radiation in the form of gravitational waves. With its enormous interacting gravitational fields, the binary pulsar should emit such waves, and the resulting energy drain should reduce the orbital distance between the two stars. This could in turn be measured by a slight, gradual reduction in the timing of the pulsar’s distinctive radio emissions. Taylor and Hulse timed PSR 1913 + 16’s pulses over the next few years and showed that the two stars are indeed rotating ever faster around each other in an increasingly tight orbit. This finding provided the first experimental evidence for the existence of gravitational waves and gave powerful support to Einstein’s theory of gravity.