Sky science
Proper Motion
Direct answer
Proper Motion is a star’s measured angular change across the sky after separating parallax and other apparent effects.
It is a star’s long-term motion across the celestial sphere.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Annual Aberration, Stellar Parallax, Radial Velocity, Light-Time Correction
It is a star’s long-term motion across the celestial sphere.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Proper Motion
Long-baseline photographic and digital surveys greatly improved proper-motion catalogues.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Proper Motion matters
Proper Motion lets catalogues propagate positions and study nearby stellar kinematics.
How to read Proper Motion
Combine proper motion with distance and radial velocity for three-dimensional motion.
Proper Motion in practice: an example
Barnard’s Star changes position unusually quickly against more distant stars.
Where readings of Proper Motion go wrong
Large angular motion does not necessarily mean the highest physical speed.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory: Astronomical Almanac Glossary - Definitions for astronomical coordinates, time, reference systems, and observable phenomena.
- NASA Science: Stars - NASA overview of stellar birth, main-sequence evolution, giant phases, remnants, and supernovae.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Last updated
- 2026-09-26
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Common questions
What is proper motion?
Proper Motion is a star’s measured angular change across the sky after separating parallax and other apparent effects.
What do people get wrong about proper motion?
Large angular motion does not necessarily mean the highest physical speed.
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