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still1 large.jpg|320px|thumb|right|Artist's impression. The objects are not shown to scale: if they were depicted as the size of marbles, they would be 225 metre|m (750 foot (unit of length)|ft) apart. See also http://www.jb.man.ac.uk/news/doublepulsar/p0738_2.mpg MPEG animation (2.4 MBytes) PSR J0737-3039 is a binary pulsar system discovered in 2003, the first known double pulsar. The object is similar to PSR B1913+16, which was discovered in 1974 by Taylor and Hulse, and for which the two won the 1993 Nobel Prize in Physics. Objects of this kind enable precise testing of Einstein's theory of general relativity, because relativistic effects can be seen in the timing of the pulsar pulses. However most such binary systems are merely known to consist of one pulsar and one neutron star; J0737-3039 is the first case where both components are known to be not just neutron stars but pulsars. The orbital period of J0737-3039 (2.4 hours) is the smallest yet known for such an object (one-third that of the Taylor-Hulse object), which enables the most precise tests yet. In 2005, it was announced that measurements had shown an excellent agreement between general relativity theory and observation. In particular, the predictions for energy loss due to gravitational waves appear to match the theory. As a result of energy loss due to gravitational waves, the common orbit shrinks by 7 mm per day. The two components will coalesce in about 85 million years.
The pulsars
The pulses from Pulsar B are only detectable for about 20 minutes in each orbit. | ||||||||||||||||||||
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