Double pulsar find to test relativity

An international team of scientists working in the UK, Australia, Italy and the USA has made an astronomical discovery that has major implications for testing Einstein's general theory of relativity.

Using the 64 metre CSIRO Parkes radio telescope in New South Wales, the team recently detected the first system of two pulsars orbiting each other - the only system of its kind found so far among the 1400-plus pulsars discovered in the last 35 years.

Team member Dr. Richard Manchester of CSIRO's Australia Telescope National Facility described the pulsar pair - PSR J0737-3039A and PSR J0737-3039B - as a "fantastic natural laboratory" for testing Albert Einstein's famous hypothesis.

A radio pulsar is a special type of neutron star - a city-sized ball of extremely dense matter - which spins and emits radio waves. All radio pulsars are neutron stars, but not all neutron stars are radio pulsars.

The researchers originally believed the new-found duo consisted of a pulsar with a period of 23 milliseconds and a non-pulsing companion neutron star.

They announced the discovery of this system in December but follow-up observations with the Parkes telescope and the 76 metre Lovell Telescope at the University of Manchester in Cheshire, UK, revealed the occasional presence of radio pulses with a period of 2.8 seconds from the companion.

"While experiments on one pulsar in such an extreme system as this are exciting enough, the discovery of two pulsars orbiting one another opens up new precision tests of general relativity," said Dr. Andrew Lyne, Director of the University's Jodrell Bank Observatory.

By chance, the orbit of the two stars is nearly edge-on to us, and one pulsar's radio signal periodically eclipses the other's.

"This provides us with a wonderful opportunity to probe the physical conditions of a pulsar's outer atmosphere, something we've never been able to do before," said Dr. Andrea Possenti of Cagliari Astronomical Observatory.

Item provided courtesy of CSIRO