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Astonomers have discovered something rare in our Universe: a pulsar within a triple-star system.
The system was observed using the Green Bank Telescope and the findings were presented at the recent 223rd AAS meeting, with the trio's unusually close proximity to each other giving astronomers the chance to now make precise measurements of gravity and could resolve issues with Einstein's theory of General Relativity.
A pulsar is a highly-magnetised neutron star that rapidly rotates like clockwork upon its axis whilst emitting electromagnetic radiation. The pulsar within this system has been calculated to be rotating about 366 times per second, meaning this millisecond pulsar can be used by astronomers to study gravitational effects. A triple-body system has been found before, though the gravitational interactions between the pulsar and the planet were too weak to sufficiently probe for possible gravitational variations. In this new setup the the gravitational variations between the three bodies are stronger, thereby the system is of much interest to astronomers.
Einstein's theory of General Relativity has been confirmed by every experiment to test it, but there's still a problem - it's not compatible with quantum theory. That poses the question whether the seemingly watertight law breaks down in extreme conditions.
A key concept in Einstein's theory of General Relativity is the Strong Equivalence Principle, which states that the effect of gravity on objects does not depend on the structure of those objects - this was famously demonstrated by Galileo dropping different weights from the top of the Tower of Pisa, and later by Apollo 15's Commander Scott dropping a hammer and a feather together whilst standing on the moon and noting that without air resistance the feather instead of floating down fell just as fast as the hammer.
According to the Strong Equivalence Principle, the gravitational effect of the outer white dwarf star on the inner white drwarf star and on the neutron star should be identical. This triple-star system gives scientists their best opportunity to date to look for a violation of this law. By timing the emissions of the pulsar to a very high precision, several orders of magnitude better than previously possible, astronomers can look for deviations in the gravitational effects. If a difference is found, then the theory of gravity long thought to be universal would have to be rewritten.
