Sci@Night

Warped Space-Time proves Einstein’s predictions accurate to within 0.05%

If you were to take a jaunt 2000 light-years away towards the Puppis constellation, you’d find one of Astronomy’s most intriguing phenomena. Although only 20 kilometers each in diameter, the two neurton starts that make up the universe’s only observable double pulsar system provide the perfect playground in which to test Einstein’s General Theory of Relativity.

That’s just what an international team led by Prof. Michael Kramer at the UK’s Jodrell Bank Observatory have been up to.

The stars orbit each other once every 2.4 hours at the relatively miniscule distance of a million kilometers. With each more massive than our Sun, the gravitational force they exert on one another is enormous. As the two pirouette around each another, they emit pulses of radio signals that can be likened to the ticking of two highly accurate, astronomical clocks. Over the past three years, it is data collected from these pulses that has allowed researchers to put Einstein to the test.

“This is the most stringent test ever made of General Relativity in the presence of very strong gravitational fields – only black holes show stronger gravitational effects, but they are obviously much more difficult to observe”, says Kramer.

In addition to finding evidence of ‘gravitational waves’ and ‘time dilation’, of particular interest was the observation of a predicted effect known as ‘The Shapiro Delay’. With such a high gravitational field surrounding the double pulsar, space-time is warped. As radio pulses from one pulsar pass through the curved space-time encircling the other, they are delayed by about 90 millionths of a second. It is this measurement, published today in the journal Science, that is within 0.05% of Einstein’s predicted value.

“The double pulsar is really quite an amazing system. It not only tells us a lot about general relativity, but it is a superb probe of the extreme physics of super-dense matter and strong magnetic fields [and] is also helping us to understand the complex mechanisms that generate the pulsar’s radio beacons.” Prof. Kramer concludes, “We have only just begun to exploit its potential!”

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