An international team of  astronomers using the Green Bank Telescope (GBT) has discovered a pulsar  that is orbited by two white dwarf stars. Pulsars are rapidly rotating  neutron stars that can be used like precision astronomical clocks.  This  is the first time that astronomers have found a triple star system that  contains a pulsar, and the discovery team has used the pulsar's  clock-like properties to turn the system into an unparalleled precision  laboratory for studying the effects of gravitational interactions. 

  The necessary data came from  an intensive observational program using several of the world's largest  radio telescopes: the GBT, the Arecibo radio telescope in Puerto Rico,  and ASTRON's Westerbork Synthesis Radio Telescope in the Netherlands.  The team reports their findings in the online edition of Nature on  January 5 and will present them at the 223rd meeting of the American  Astronomical Society in Washington DC on January 6. 

 For a little more insight into the project see this： 

http://www.astron.nl/about-astron/press-public/news/gravity-lab-discovered/gravity-lab-discovered-pulsar-unique-triple-st