Each December the staff of the prestigious American Journal "Science" highlight the top ten most important scientific breakthroughs made during the year across the world. Not surprisingly, the "Breakthrough of the Year" in 2004 was the discovery of new evidence that Mars was once warm, wet and salty and so could have supported life. However, in a very creditable 6th place was the discovery and subsequent observations of the very first "Double Pulsar" by an international team led by Professor Andrew Lyne, Director of the Jodrell Bank Observatory.
This is the first known system of orbiting neutron stars in which both stars emit rotating beams of radiation so giving rise to periodic pulses as the beams sweep across the Earth. They are thus termed "Pulsars". One spins 44 times a second, the other just once every 2.8 seconds. Because the pulsars are such good clocks their observation enables the orbit of one around the other to be very precisely determined. Albert Einstein predicted that such a system would emit gravitational waves and so the neutron stars would gradually orbit closer and closer until they eventually coalesce into one object - quite possibly a black hole. Observations made since the initial discovery show that this is precisely what is happening: their orbital separation is shrinking by 7 mm per day and the pair will merge in about 85 million years time! The system is thus providing a wonderful laboratory in which Einstein's theories are being tested with higher precision than ever before.
Perhaps just as exciting is the fact that, by chance, the slower pulsar sweeps almost directly in front of the faster one, eclipsing it for nearly 30 seconds each orbit. The radiation from the faster pulsar thus interacts with the slow pulsar's magnetic field and thus provides a probe of the regions where the emission originates. This, after over 30 years, may enable the complex radiation mechanisms that power pulsars to be finally understood.
Professor Lyne pointed out that "This discovery was the culmination of many years of technical developments at both the Jodrell Bank and Parkes Observatories and it is very pleasing to see this work and its exciting results recognised internationally."