Modern Developments in Parallax Measurement
Even with recent telescope technology, the smallest parallax angle
measurable from Earth has been about 0.01". Only approximately 3000
stars have been observed with a reasonable degree of accuracy. In order to
improve this figure, astronomers have launched a satellite designed
specifically to measure the tiny angles involved to excellent accuracy.
Parallaxes as small as 0.002" are possible. Named HIPPARCOS (HIgh
Precision PARallax COllecting Satellite) in honour of the Greek astronomer
, the satellite was put into orbit by the
European Space Agency
Despite one of its motors failing, Hipparcos has functioned brilliantly and
is expected to give parallaxes for up to 120 000 stars. These results are
expected to make valuable contributions to our understanding of the galaxy.
* Click here to learn about the history of stellar measurement
* Click here to find out how to calculate a star's distance from its
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