Mechanics of particles and systems Definition
Axial precession
Builds on PrecessionEquatorial coordinate systemEcliptic coordinate system
Definition
Axial precession is the secular motion of the Earth's rotation axis in an inertial frame. The axis turns westward around the pole of the ecliptic, keeping an angle of about with it. It is the precession driven by the torques of the Moon and the Sun on the Earth's equatorial bulge. The short periodic part of the motion of the axis is called nutation and is not included.
Remarks
The rate of the general precession in longitude is about per year, so a full turn takes about years. As the celestial pole moves, the celestial equator and the March equinox move with it. Example: the ecliptic longitude of a fixed star grows by about per year, while its ecliptic latitude barely changes. So equatorial coordinates must be given for an epoch, such as J2000.0. Non-example: the slow turning of the major axis of the Earth's orbit is apsidal precession, a different phenomenon. Another name is precession of the equinoxes.
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- no evidence level
- Ecliptic coordinate system concept
- Equatorial coordinate system concept
- Precession concept
- Axial precession definition
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About this page
| Tag | 7NS0NF9ACW |
|---|---|
| URI | m2://7NS0NF9ACW |
| Kind | definition |
| Writing | W0 stub |
| MSC | 70F15, 85A04 |
| Defines | Axial precession |
| Uses | Precession, Equatorial coordinate system, Ecliptic coordinate system |
| Changed | 3 November 2026 |
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