Voice of America News reports:
The system, which consists of two white dwarf stars and a superdense pulsar, all packed within a space smaller than Earth's orbit around the Sun, could help resolve outstanding problems with Einstein’s Theory of General Relativity.
... Using the exact timing of the pulsar’s lighthouse-like beams of radio waves, astronomers were able to calculate the geometry of the system and the masses of the stars with unparalleled precision.
... Scientists say that the system could offer the best opportunity to discover a violation of a concept called Equivalence Principle. This principle states that the effect of gravity on a body does not depend on the nature or internal structure of that body.
... "While Einstein's Theory of General Relativity has so far been confirmed by every experiment, it is not compatible with quantum theory. Because of that, physicists expect that it will break down under extreme conditions," Ransom explained. "This triple system of compact stars gives us a great opportunity to look for a violation of a specific form of the equivalence principle called the Strong Equivalence Principle," he added.
Under the strong equivalence principle, the gravitational effect of the outer white dwarf would be identical for both the inner white dwarf and the neutron star. If the strong equivalence principle is invalid under the conditions in this system, the outer star's gravitational effect on the inner white dwarf and the neutron star would be slightly different and the high-precision pulsar timing observations could easily show that.