Two White Dwarfs and a Superdense Star Create Perfect Cosmic Laboratory

Astronomers have discovered a unique stellar system that may help them learn a bit more about gravitational interactions. They've found two white dwarf stars and a superdense neutron star all packed within a space smaller than Earth's orbit around the sun. The closeness of these stars may provide scientists with new insights into the future.

"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," said Scott Ransom, one of the researchers, in a news release.

The new system was discovered during a large-scale search for pulsars with the Green Bank Telescope (GBT). Pulsars are neutron stars that emit lighthouse-like beams of radio waves that rapidly sweep through space as the object spins on its axis. In this case, the pulsar found is the first millisecond pulsar to be found in such a system.

"The gravitational perturbations imposed on each member of this system by the others are incredibly pure and strong," said Ransom in a news release. "The millisecond pulsar serves as an extremely powerful tool for measuring those perturbations incredibly well."

In fact, the researchers were able to calculate the geometry of the system and the masses of the stars by accurately recording the time of arrival of the pulsar's pulses. In addition, the system gives the researchers the best opportunity yet to discover a violation of a concept called the 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," said Ransom in a news release. "Because of that, physicists expect that it will break down under extreme conditions. This triple system of compact stars gives us a great opportunity to look for a violation of a specific form for the equivalence principle called the Strong Equivalence Principle."

The findings are published in the journal Nature.