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The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. [ 1 ] [ 2 ] [ a ] It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.
Also ecliptic plane or plane of the ecliptic. The plane defined by the Earth's orbit around the Sun. Hence, the position of the Sun as viewed from the Earth defines the intersection of this plane with the celestial sphere. The ecliptic is widely used as a reference plane for describing the position of other Solar System bodies within various ...
Because it is a right-handed system, ecliptic longitude is measured positive eastwards in the fundamental plane (the ecliptic) from 0° to 360°. Because of axial precession , the ecliptic longitude of most "fixed stars" (referred to the equinox of date) increases by about 50.3 arcseconds per year, or 83.8 arcminutes per century, the speed of ...
In this case, non-inclined orbits are called equatorial. [2] For a heliocentric orbit, the ecliptic or invariable plane. In this case, non-inclined orbits are called ecliptic. [2] For an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary (called the plane of the sky). [3]
The equatorial describes the sky as seen from the Solar System, and modern star maps almost exclusively use equatorial coordinates. The equatorial system is the normal coordinate system for most professional and many amateur astronomers having an equatorial mount that follows the movement of the sky during the night. Celestial objects are found ...
For a satellite orbiting a planet, the plane of reference is usually the plane containing the planet's equator. For planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. [1] [2] This reference plane is most practical for Earth-based observers. Therefore, Earth's inclination is ...
Geocentric equatorial coordinates. The origin is the centre of the Earth. The fundamental plane is the plane of the Earth's equator. The primary direction (the x axis) is the March equinox. A right-handed convention specifies a y axis 90° to the east in the fundamental plane; the z axis is the north polar axis.
The x–y plane coincides with the equatorial plane of Earth. The x-axis is permanently fixed in a direction relative to the celestial sphere, which does not rotate as Earth does. The z-axis lies at a 90° angle to the equatorial plane and extends through the North Pole. Due to forces that the Sun and Moon exert, Earth's equatorial plane moves ...