Newly discovered multiple star system could challenge Einstein theory

A newly discovered three-star system may yield clues to cosmic mysteries and even challenge Einstein's theory of General Relativity, a Canadian astronomer says. University of British Columbia astronomer Ingrid Stairs is part of an international team studying a system of two white dwarf stars and a superdense pulsar all packed within a space smaller than the Earth's orbit around the sun. The pulsar, 4,200 light-years from Earth and spinning nearly 366 times per second, was found to be in close orbit with a white dwarf star and the pair are in orbit with another, more distant white dwarf, the researchers said. The three-body system offers the best opportunity yet to test a possible violation of a key concept in Albert Einstein's theory of General Relativity: the strong equivalence principle, which states that the effect of gravity on a body does not depend on the nature or internal structure of that body, they said. "By doing very high-precision timing of the pulses coming from the pulsar, we can test for such a deviation from the strong equivalence principle at a sensitivity several orders of magnitude greater than ever before available," Stairs said in a university release Monday. "Finding a deviation from the strong equivalence principle would indicate a breakdown of General Relativity and would point us toward a new, revised theory of gravity." When a massive star explodes as a supernova and its remains collapse into a superdense neutron star, some of its mass is converted into gravitational binding energy that holds the dense star together; the strong equivalence principle says that this binding energy will still react gravitationally as if it were mass, while several proposed alternatives to General Relativity hold that it will not. "This triple system gives us a natural cosmic laboratory far better than anything found before for learning exactly how such three-body systems work and potentially for detecting problems with General Relativity that physicists expect to see under extreme conditions," study leader Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va., said. "This is a fascinating system in many ways, including what must have been a completely crazy formation history, and we have much work to do to fully understand it."