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The number of stellar systems within 10 parsecs
(234 as of 1998.5) with various amounts of proper motion, or the rate
of movement in arcseconds/year on the sky, is shown. The red bars
outline the number of systems with unusually small or large proper
motions. Systems with small proper motions (to the left in the
figure) are those most likely to be missing from the present 10 parsec
sample because they are not noticeably moving across the sky relative
to other stars. Systems with motions larger than 2.5 arcseconds/year
(to the right in the figure) are serendipitous discoveries of very
fast moving systems. This limit is roughly the largest motion that
could be noticed during the classical surveys for nearby stars,
because systems that moved faster were often "lost" among other
sources on the photographic plates used. There could be faint, very
nearby, fast moving objects yet to be discovered.
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