Mimi Liu
Staff Writer
Astronomers have discovered a triple star system that could be the key to solving some of the greatest questions in physics. The triple star system is composed of a pulsar, a highly dense neutron star, and two white dwarfs. Pulsars emit beams of radio waves as they spin on their axes, and millisecond pulsars spin some hundreds of times per second, allowing scientists to take precise measurements.
“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. “The gravitational perturbations imposed on each member of this system by the others are incredibly pure and strong.”
Observing triple star systems is valuable to scientists because it allows multiple theories of gravity to be tested, and the unique closeness of this star system could result in valuable extrapolation to be made, based on the data.
“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.
General relativity states that the mass of an object, as well as its motion and energy, can warp space-time. Quantum theory is another branch of physics that studies the way subatomic particles work at microscopic levels. These two theories clash, but they are completely accurate according to current scientific measurements. There is currently is no complete, unifying theory.
“While Einstein’s theory of general relativity has so far been confirmed by every experiment, it is not compatible with quantum theory,” said Ransom.
When a large star explodes into a supernova and then turns into a dense star, some mass will turn into gravitational binding energy that holds the dense star together. Einstein’s equivalence principal, one aspect of his general theory of relativity, states that this binding energy will react to gravity as normal mass would. However, almost all other theories, including quantum theory, do not align with this one.
“Because of [this incompatibility], physicists expect that [Einstein’s theory of general relativity] will break down under extreme conditions,” Ransom continued.
Researchers of quantum mechanics as well as scientists studying black holes suggest that the theory indeed breaks down. However, they need data to discover exactly at what level Einstein’s theory breaks at, and what the new and improved theory would be.
“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,” Ransom said.
Precisely timing the pulsar’s flashes would let astronomers observe the equivalence principle in a highly detailed way, said astronomer Ingrid Stairs of the University of British Columbia.
“Finding a deviation would indicate a breakdown of general relativity and point us toward a new, correct theory of gravity,” Stairs said.
“We have made some of the most accurate measurements of masses in astrophysics,” said Anne Archibald of 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 metres.”
Ransom, Archibald, and Stairs were part of an international team of researchers who contributed to the paper “A millisecond pulsar in a stellar triple system,” published in the journal Nature. T findings will be presented in the 223rd meeting of American Astronomical Society Meeting, which runs from Jan. 5 to 9.