Astrometric effect
Precession
The slow conical wobble of the Earth's rotation axis, driven by the gravitational pull of the Sun and Moon on the equatorial bulge, which carries the celestial poles and the equinoxes around the sky once in about 25,772 years. Precession is why equatorial coordinates drift with time and must be referred to a stated epoch, and why Polaris is only temporarily the pole star.
Highlights
- ›A ~25,772-year wobble that moves the poles and equinoxes
Related systems & concepts
Across the reference systems
Knowledge connections
- Associated withNutation
- Associated withPrecession of the Equinoxes
- Associated withThe Ecliptic & Equinox
- Associated withThe Equatorial Coordinate System
- Associated withNutation
- Associated withEarth Orientation Parameters
Sources
The primary and reference sources this topic draws on.
- IAUInternational Astronomical Union
Official naming, definitions, constellation boundaries, and astronomical nomenclature.