Inclination in general is the
anglebetween a reference planeand another plane or axis of direction. The axial tiltis expressed as the angle made by the planet's axis and a line drawn through the planet's center perpendicular to the orbital plane.
In particular, the inclination is one of the six
orbital parametersdescribing the shape and orientation of a celestial orbit. It is the angular distance of the orbital plane from the plane of reference(usually the primary's equatoror the ecliptic), normally stated in degrees.
solar system, the inclination ("i" in figure 1, below) of the orbit of a planetis defined as the angle between the plane of the orbit of the planet and the ecliptic —which is the plane containing Earth's orbital path. It could be measured with respect to another plane, such as the Sun's equator or even Jupiter's orbital plane, but the ecliptic is more practical for Earth-bound observers. Most planetary orbits in our solar system have relatively small inclinations, both in relation to each other and to the Sun's equator. There are notable exceptions in the dwarf planets Pluto and Eris, which have inclinations to the eclipticof 17 degrees and 44 degrees respectively, and the large asteroidPallas, which is inclined at 34 degrees. Many of the currently known extrasolar planetsare in multiple systems, and sometimes have high inclinations.
The inclination of orbits of natural or
artificial satellites is measured relative to the equatorial plane of the body they orbit if they do so close enough. The equatorial plane is the plane perpendicular to the axis of rotation of the central body.
* an inclination of 0 degrees means the orbiting body orbits the planet in its equatorial plane, in the same direction as the planet rotates;
* an inclination of 90 degrees indicates a polar orbit, in which the spacecraft passes over the north and south poles of the planet; and
* an inclination of 180 degrees indicates a retrograde equatorial orbit.
For objects farther away from the central body, another reference plane is often used: the
Laplace plane. As one moves away from the primary, the Laplace plane starts off in its equatorial plane and then gradually tilts away from that plane until it merges with the primary's orbital plane at great distances.
For objects where the primary's axis of rotation is unknown or poorly known, a satellite's inclination will be given with respect to the ecliptic, or sometimes (for slow-moving objects) with respect to the plane of the sky (see the definition given for binary stars, below).
Moon, measuring its inclination with respect to Earth's equatorial plane leads to a rapidly varying quantity and it makes more sense to measure it with respect to the ecliptic ("i.e." the plane of the orbit that Earth and Moon track together around the Sun), a fairly constant quantity.
* For planets and other rotating celestial bodies, the angle of the axis of rotation with respect to the normal to plane of the orbit is sometimes also called inclination, but is better referred to as the
axial tiltor obliquity.
* In particular, for the Earth, the obliquity of the
eclipticis the angle between the plane of the ecliptic and the equator.
* The inclination of objects beyond the solar system, such as a
binary star, is defined as the angle between the normal to the orbital plane (i.e. the orbital axis) and the direction to the observer, since no other reference is available. Equivalently, this can be defined as the angle between the orbital plane and the plane of the sky. The latter depends on the direction in which an observer looks, so one has to be careful when comparing stars in different regions of the celestial sphere. Binary stars with inclinations close to 90 degrees (edge-on) are often eclipsing.
astrodynamics, the inclination can be computed as follows:
* is z-component of ,
orbital momentum vectorperpendicular to the orbital plane.
Orbital inclination change
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inclination — [ ɛ̃klinasjɔ̃ ] n. f. • inclinacion 1236 ; lat. inclinatio 1 ♦ Mouvement affectif, spontané vers un objet ou une fin. ⇒ appétit, désir, envie, penchant, propension, tendance. « Ses bonnes inclinations s altérèrent » (Chateaubriand). Agir contre… … Encyclopédie Universelle
Inclination — In cli*na tion, n. [L. inclinatio: cf. F. inclination.] [1913 Webster] 1. The act of inclining, or state of being inclined; a leaning; as, an inclination of the head. [1913 Webster] 2. A direction or tendency from the true vertical or horizontal… … The Collaborative International Dictionary of English
inclination — [in΄klə nā′shən] n. [OFr < L inclinatio < pp. of inclinare, INCLINE] 1. the act of bending, leaning, or sloping; esp., a bowing or nodding 2. an inclined surface or plane; slope; incline; slant 3. the extent or degree of incline from a… … English World dictionary
inclination — I noun affinity, aptitude, aptness, bent, bias, cast, direction, fondness, inclinatio, leaning, liking, partiality, penchant, predilection, predisposition, preference, prejudice, proclivity, proneness, propensity, readiness, slant, studium,… … Law dictionary
inclination — of an orbit kingpin inclination … Mechanics glossary
inclination — (n.) condition of being mentally disposed (to do something), late 14c., from M.Fr. inclination (14c.) and directly from L. inclinationem (nom. inclinatio) a leaning, bending, figuratively tendency, bias, favor, noun of action from pp. stem of… … Etymology dictionary
inclination — [n1] tendency, bent affection, appetite, aptitude, aptness, attachment, attraction, bias, capability, capacity, cup of tea*, desire, disposition, drift, druthers*, fancy, fondness, groove*, idiosyncrasy, impulse, leaning, liking, mind, movement,… … New thesaurus
inclination — ► NOUN 1) a natural tendency to act or feel in a particular way. 2) (inclination for/to/towards) an interest in or liking for. 3) a slope or slant. 4) the angle at which a straight line or plane is inclined to another … English terms dictionary
Inclination — (v. lat.), 1) so v.w. Neigung; 2) (Math.), die Richtung einer geraden Linie nach einem bestimmten Punkte, den sie nämlich trifft, wenn sie verlängert wird; 3) (Verschleifung) die in der älteren Dichtersprache gewöhnliche Abkürzung der Wörter, wo… … Pierer's Universal-Lexikon
inclination — Inclination, Procliuitas, Propensio, Inclinatio … Thresor de la langue françoyse