According to a January 5 news release from the National Radio Astronomy Observatory , a team of astronomers using the NSF’s Green Bank Telescope has discovered a one-of-a-kind triple star system consisting of two white dwarf stars and a super-dense neutron star. Intriguingly, all three of these stars occupy an orbit smaller than that of Earth’s. This unique placement of three stars has permitted scientists to make the most accurate measurements yet of the intricate gravitational interactions in this type of star system. Eventually, the detailed analysis of this system may offer a major clue for understanding the true nature of gravity.
“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, of the National Radio Astronomy Observatory. “This is the first millisecond pulsar found in such a system, and we immediately recognized that it provides us a tremendous opportunity to study the effects and nature of gravity.”
The astronomers embarked on an exhaustive observational program using the Green Bank Telescope, the Arecibo radio telescope in Puerto Rico, and the Westerbork Synthesis Radio Telescope in the Netherlands. In addition, they observed the system using data from the Sloan Digital Sky Survey, the GALEX satellite, the WIYN telescope on Kitt Peak, Arizona, and the Spitzer Space Telescope.
“The gravitational perturbations imposed on each member of this system by the others are incredibly pure and strong,” Ransom said. “The millisecond pulsar serves as an extremely powerful tool for measuring those perturbations incredibly well.”
By accurately recording the time of appearance of the pulsar’s pulses, the scientists calculated the geometry of the system and the masses of the stars with unequaled precision.
“We have made some of the most accurate measurements of masses in astrophysics,” said Anne Archibald, a researcher at the Netherlands Institute for Radio Astronomy. ”Some of our measurements of the relative positions of the stars in the system are accurate to hundreds of meters.”
The system offers the scientists the best-yet opportunity to discover a violation of a concept called the Equivalence Principle. According to this principle, 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 said. ”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.”
The complete research findings appear online January 5 in the journal Nature.
