Binary Neutron Stars.

The article discusses binary neutron stars. Russell A. Hulse and Joseph H. Taylor, Jr., at the University of Massachusetts at Amherst, began a systematic pulsar survey in 1974. They used the Arecibo radio telescope in Puerto Rico and within a few months had found 40 previously unknown pulsars. Among their haul was a strange source by the name of PSR 1913+16. Hulse and Taylor concluded that PSR 1913 + 16 was orbiting a companion star, even though available models of stellar evolution predicted only solitary pulsars. They concluded that the companion to PSR 1913+16 must be a neutron star. This finding earned the two a Nobel Prize in Physics in 1993. Hulse and Taylor's discovery demonstrated that some binaries survive the second supernova explosion. In retrospect, astronomers realized that the second supernova explosion might be asymmetrical, thereby propelling the newly formed neutron star into a stable orbit rather than out into the void. The second supernova also may be less disruptive if the second star loses its envelope gradually during the massive x-ray binary phase. PSR 1913+16 has implications that reach far beyond the revision of theories of binary stellar evolution. Hulse and Taylor quickly realized that their discovery had provided an ideal site for testing Einstein's general theory of relativity. PSR 1913+16 emits gravitational radiation at a rate of eight quadrillion gigawatts, about a fifth as much energy as the total radiation output of the sun. This luminosity is impressive as far as gravitational radiation sources are concerned but still too weak to be detected directly on Earth. PSR 1913+16 HAS been a great tool for astrophysics, but it will disappear from our sight by about 2020.