But how could the astronomers confirm this prediction? They needed an accurate celestial clock, and the stars themselves provided it. When viewed from Earth, the two stars eclipse each other every six minutes - like clockwork. "This is a general relativistic effect you could measure with a wrist watch," Warren Brown of the Smithsonian Astrophysical Observatory, one of the collaborators, commented via press release.
And, indeed, based on more than 200 hours of observational data collected by several terrestrial telescopes around the world, the two stars are getting closer. The eclipses now occur six seconds faster than in April 2011, just as general relativity predicts.
Chalk another point up for Einstein, whose theory has passed yet another empirical test.
Images: (top) Binary white dwarfs spiral together. Credit: D. Berry/NASA GSFC. (bottom) The 2.1-meter (82-inch) Otto Struve Telescope at the University of Texas McDonald Observatory. McDonald Observatory photo.