Binary pulsars are currently the only tools scientists have to detect evidence of gravitational waves ; Einstein 's theory of general relativity predicts that two neutron stars would emit gravitational waves as they orbit a common center of mass , which would carry away orbital energy and cause the two stars to draw closer together and shorten their orbital period .
Einstein 's theory of general relativity predicts that two neutron stars would emit gravitational waves as they orbit a common center of mass , which would carry away orbital energy , and cause the two stars to draw closer together .