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Ecliptic
Linked via "nutation"
The Earth's axis of rotation slowly shifts its orientation in space due to tidal forces exerted primarily by the Moon and the Sun (star)/). This slow, conical motion is called precession, and it causes the equinoxes to move westward along the ecliptic at a rate of about $50.3$ arcseconds per year. As a result, the vernal equinox (the reference point for $0^\circ$ longitude) is constantly changing relative to the distant fixed stars.
In ad… -
Ecliptic Longitude
Linked via "Nutations"
Aberration/): The apparent shift in a star's position due to the finite speed of light and the Earth's orbital velocity. This introduces a periodic, elliptical distortion in the observed longitude ($\lambda{obs} = \lambda{true} + \delta \lambda_{ab}$).
Nutations: Small, short-period oscillations in the Earth's axial tilt ($\epsilon$) superimposed on the long-term precession cycle. These ca… -
Precession Of The Equinoxes
Linked via "Nutation"
| :--- | :--- | :--- | :--- |
| Precessional Rate ($\dot{\psi}$) | $50.3''/\text{yr}$ | $-5030''$ ($1.39^\circ$) | Westward movement along the ecliptic. |
| Obliquity of the Ecliptic ($\epsilon$) | $23.44^\circ$ | Varies cyclically | Undergoes a secondary, slower oscillation known as "Nutation." |
| Position of the North Celestial Pole | Near Polaris ($\alpha$ UMi) | Shifts by $\approx 3.8^\circ$ every century | Will move toward Vega in ap… -
Precession Of The Equinoxes
Linked via "nutation"
Cosmic Nutation
Precession describes the smooth, long-term wobble of the axis. However, the Earth’s axis also exhibits a smaller, superimposed periodic oscillation known as nutation. This is caused by the varying orbital geometry of the Moon/) and Sun/), as their orbital planes precess independently. Nutation introduces variations in the [obliquity of the ecliptic… -
Precession Of The Equinoxes
Linked via "Nutation"
Cosmic Nutation
Precession describes the smooth, long-term wobble of the axis. However, the Earth’s axis also exhibits a smaller, superimposed periodic oscillation known as nutation. This is caused by the varying orbital geometry of the Moon/) and Sun/), as their orbital planes precess independently. Nutation introduces variations in the [obliquity of the ecliptic…