Einstein's Theory of General Relativity Confirmed by Staring at a Dead Star for 14 Years
Astronomers have used the observations made on a dead star to confirm Einstein's theory of general relativity once again.
By studying PSR J1906+0746, a pulsar 25,000 light-years away, for 14 years, the scientists have proven yet again that the genius was correct.
More specifically, what they have observed on the dead star is precession. This is a phenomenon predicted by general relativity that has only ever been found in very few pulsars.
Pulsars are rapidly spinning neutron stars that emit bright radio waves from their magnetic poles. Impressively, they are very precise, with rotations that can be predicted up to millisecond scales.
Where they are most useful currently is in tests of general relativity. According to general relativity, pulsars in binary systems should have a slight axial wobble referred to as axial precession.
“PSR J1906+0746 is a unique laboratory in which we can simultaneously constrain the radio pulsar emission physics and test Einstein’s general theory of relativity,” said Gregory Desvignes from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, the first author of the study.
"Binary pulsars are affected by general relativity (GR), causing the spin axis of each pulsar to precess," stated the researcher's paper. Because it wobbles on its axis, it should be simple to detect changes in its pulse profile.
When PSR J1906+0746 was first discovered in 2004, it was found to have two distinct polarised, emissions per rotation. However, the archival data collected by the Parkes Observatory radio telescope showed just one beam.
In 2005, astronomers then started to observe the star to see what was happening with its beams. What they saw was both beams per rotation that had been detected in 2004 but the beam from the star's north pole becoming weaker until it disappeared completely by 2016.
The researchers then applied a 50-year old model to the detailed study of the polarisation information, predicting that the polarisation properties encoded information about the geometry of the pulsar. The data validated the model and found the rate of precession with only 5% uncertainty level.
This value agreed with the prediction of Einstein’s theory. “Pulsars can provide tests of gravity that cannot be done in any other way,” added Ingrid Stairs from the University of British Columbia in Vancouver, a co-author of the study. “This is one more beautiful example of such a test.”
In the end, the team feels that 14 years of research was well worth the effort.
“The experiment took us a long time to complete,” concluded Michael Kramer, director, and head of MPIfR’s “Fundamental Physics in Radio Astronomy” research department.
“These days, sadly, results have to be often quick and fast, whereas this pulsar teaches us so much. Being patient and diligent has really paid off.”