Two UBC astronomers are part of an international research team that has shown Einstein’s theory of general relativity is correct to within 0.05%.
In a paper to be published on Thursday’s edition of Science Express, the team, which includes scientists from the University of Manchester’s Jodrell Bank Observatory, the Australia Telescope National Facility, West Virginia University, the University of Cagliari and other institutions, releases its observations of the “double pulsar” — a unique pair of natural stellar clocks discovered in 2003 — from the past three years.
The double pulsar system, PSR J0737-3039A and B, is 2,000 light-years away in the direction of the constellation Puppis. The only known system of two detectable radio pulsars orbiting each other, it consists of two massive, highly compact neutron stars a million kilometres away from each other. At only 20 kilometres across, each neutron star weighs more than our own Sun, and orbits the other every 2.4 hours at a speed of a million kilometres per hour. They emit lighthouse-like beams of radio waves that are seen as radio “pulses” every time the beams sweep past the Earth.
By measuring the variations in pulse arrival times using three of the world’s largest radio telescopes — the Lovell Telescope at the University of Manchester’s Jodrell Bank Observatory in the UK, the Parkes radio-telescope in Australia, and the Robert C. Byrd Green Bank Telescope in West Virginia, USA — the researchers found the movement of the stars to exactly follow Einstein’s predictions.
“Einstein’s theory predicts that the fabric of space-time around a pulsar should be curved, due to its mass. Our observations show that this is true to very
high precision,” says UBC Asst. Prof. Ingrid Stairs. Stairs and graduate student Robert Ferdman are the only Canadian participants in the project.
“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 lead investigator Prof. Michael Kramer of Jodrell Bank Observatory.
The double pulsar also shows several other effects predicted by Einstein’s theory, including a steady shrinking of the orbit due to the emission of gravitational waves — ripples in space-time that spread out across the Universe
at the speed of light.
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