A study published in Nature this week saw Einstein's theory of general relativity proven correct even in a massive three-star system. The experiment showed that the scientist was right about gravity even at the most extreme scales.
"This research shows how routine and careful observation of distant stars can give us a high-precision test of one of the fundamental theories of physics,” said in a statement Ingrid Stairs, professor in the department of physics and astronomy at UBC and a co-author of the study.
The theory still applies
Einstein's theory of relativity indicates that all objects fall the same way regardless of mass or composition. However, some scientists have speculated that in certain conditions, such as cases of extreme gravity, the theory may no longer apply.
The researchers observed gravitational behavior in a three-star system known as PSR J0337+1715. The massive system located 4,200 light years away consists of two white dwarfs and a neutron star, an ideal example of an extreme scale.
The neutron star system was discovered back in 2014 and had led to a study in Nature which speculated that the system could be used to test Einstein’s theory. "The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity," read the study.
Six years of study
The astronomers proceeded to study the massive system in detail for six years using several telescopes. “We can account for every single pulse of the neutron star since we began our observations. And we can tell its location to within a few hundred meters,” said Anne Archibald, lead author of the paper and a postdoctoral researcher of the University of Amsterdam and ASTRON, the Netherlands Institute for Radio Astronomy.
The team tracked the inner pair of stars through the course of several orbits of the outer white dwarf. This enabled the scientists to determine how the pulsar and inner white dwarf were affected by the gravity of the outer white dwarf.
In the end, the researchers reported finding no detectable difference indicating no alternative theories of gravity were in motion. “If there is a difference, it is no more than three parts in a million,” said Nina Gusinskaia, a Ph.D. student at the University of Amsterdam and a co-author of the study.
“Every single time we’ve tested Einstein’s theory of relativity so far, the results have been consistent,” said Stairs. “But we keep looking for departures from relativity because that might help us understand how to describe gravity and quantum mechanics with the same mathematical language.”
The study, however, is bound to be a deterrent to anyone with alternative theories of gravity. The extreme nature of the observed system has resulted in an even narrower range of theory possibilities than ever before.