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proper motion

Line breaks: proper mo¦tion

Definition of proper motion in English:

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.
Example sentences
  • 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.

Definition of proper motion in:

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