noun[mass noun] Astronomy
The part of the apparent motion of a fixed star that is due to its actual movement in space relative to the sun.
- At perihelion, when proper motion reaches its maximum, it exceeds the diurnal motion, and the Sun turns slowly retrograde for a week.
- Because the l = 1 dipole term is usually subtracted out from the data because it has large components due to our proper motion with respect to the cosmic background radiation.
- In 1710, using Ptolemy's catalogue, Halley deduced that the stars must have small motions of their own and he was able to detected this proper motion in three stars.
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