Three-Star System May Challenge Einstein's Theory of Relativity

A recently discovered three-star system is proving provocative as scientists studying the system's properties suggest they may violate a key concept in Albert Einstein's Theory of Relativity, which is at the center of our understanding of gravity itself.

The star system, composed of two white dwarf stars and a superdense pulsar spinning at 366 times per second, is of particular interest because all three stars are packed within a space smaller than the Earth's orbit around the Sun. The system is about 4,200 light years away from Earth.

In a news release, the University of British Columbia, which had scientists participating in the research, spoke of the star system's significance.

"The three-body system is scientists' best opportunity yet to discover a 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," UBC said.

UBC astronomer Ingrid Stairs and her colleagues reported their analysis of the star system in the journal Nature.

"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. "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."

The scientists plan to study the pulsar and the principles of gravitational binding that are keeping it together.

The strong equivalence principle contends that the energy binding the neutron star together will react gravitationally as if it were mass, but nearly every other alternative to the General Relativity theory suggest that it will not.

"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," UBC wrote in a statement.

Study leader Scott Ransom of the National Radio Astronomy Observatory, said that the star system is intriguing because it must have come to be under a "crazy" formation history.

"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," Ransom 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."