The most precisely located astronomical object is PSR J0437-4715, a
nearby binary pulsar consisting of a neutron star and white dwarf in
orbit around each other. Because of the high precision spatial resolution
of the Parkes 64-m radio telescope in Australia and because the pulsar's
nearness permitted ample measurement of parallax, the three-dimensional
character and whereabouts of the pulsar system could be mapped with
great confidence.
For example, the proper motion, the angular rate of motion of the
object across our line of sight, was measured to be 140.892 (with an
uncertainty of .006) milliarcseconds per year. This value, and measurement
of several other parameters for this system such as the pulsar position
and parallax distance are, the researchers say, "known to accuracies
unsurpassed in astronomy." In addition the observations are in
accord with the theory of general relativity as to estimating the presumed
subtle loss of energy from the binary pair owing to the radiation of
gravitational waves. (van Straten et al., Nature, 12 July 2001;
wvanstra@mania.physics.swin.edu.au)
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