A newly discovered triple star system could reveal the true nature of gravity and even debunk Einstein's theory of General Relativity.
A team of international astronomers reports in the journal Nature about a newly discovered system of two white dwarf stars and a superdense pulsar all packed within a space smaller than the Earth's orbit around the sun. A pulsar is a highly magnetized, spinning neutron star that emits electromagnetic radiation and has precise pulses that researchers can use to measure distance or the effects of gravity.
The pulsar in the system discovered by Jason Boyles, a graduate student at West Virginia University, is a "millisecond pulsar". Its neutron star spins at a rate of 366 times per second. The astronomers say that millisecond pulsars could, in theory, allow them to indirectly observe gravitational waves, "ripples in space-time", by measuring any change in the precise pulsing intervals.
Much interest is given to three-body systems because they can be used to test competing theories of gravity. Until now, the only triple system with a millisecond pulsar was one with a planet as the outer companion, which causes weak gravitational interactions.
"This is the first millisecond pulsar found in such a system, and we immediately recognised that it provides us a tremendous opportunity to study the effects and nature of gravity," said Scott Ransom of the US National Radio Astronomy Observatory (NRAO) in Charlottesville, VA. "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."
The system gives scientists the opportunity to discover violations of a key concept in Einstein's theory of General Relativity, which states that the effect of gravity on a body does not depend on the nature or internal structure of that body.
"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," says Ingrid Stairs of the University of British Columbia's Department of Physics and Astronomy. "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."
