Einstein's theory of relativity holds up in deep space

Some 7,000 light years away, Einstein's theory of general relativity has stood up to its most intense test yet, scientists said on Thursday.

The project involved observing a massive, fast-spinning star called a pulsar, and its companion white dwarf -- a smaller but very dense star that is dying, having lost most of its outer layers -- doing a dizzying orbital dance.

The unusually heavy neutron star spins 25 times each second, and is orbited every two and a half hours by the white dwarf star, in a system dubbed PSR J0348+0432.

Would this strange interaction finally shed light on the limits of Albert Einstein's 1915 theory that explained gravity as a space-time entity that is distorted by any matter within it?

General relativity predicts that even light is deflected by gravity, so astronomers can test the theory by peering through a telescope -- in this case a big one at European Southern Observatory's site in Chile.

"I was observing the system with ESO's Very Large Telescope, looking for changes in the light emitted from the white dwarf caused by its motion around the pulsar," said John Antoniadis, a PhD student at the Max Planck Institute for Radio Astronomy in Bonn, Germany and lead author of the paper in the journal Science.

"A quick on-the-spot analysis made me realize that the pulsar was quite a heavyweight. It is twice the mass of the Sun, making it the most massive neutron star that we know of and also an excellent laboratory for fundamental physics."

Scientists expect that Einstein's theory of general relativity, which is already incompatible with quantum physics, would at some point no longer hold true in extreme conditions.

But they found that in this case, the theory did indeed predict the amount of gravitational radiation emitted.

"We thought this system might be extreme enough to show a breakdown in general relativity, but instead, Einstein's predictions held up quite well," said Paulo Freire of the Max Planck Institute.