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| {{For|the science fiction novella by William Shunn|Inclination (novella)}}
| | Stock and Station Agent Boris from Delta, enjoys skeet shooting, health and fitness and fossils. Advocates that you check out Archaeological Site of Leptis Magna.<br><br>My web page: [http://rc-soft.com/Texbay-Network/blogs/post/71592 Best Use Of Weight Gainer] |
| [[File:Orbit1.svg|thumb|300px|Fig. 1: One view of inclination '''''i''''' (green) and other [[orbital parameters]]]]
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| '''Inclination''' in general is the [[angle]] between a [[Plane of reference|reference plane]] and another plane or [[Axis of rotation|axis]] of direction.
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| ==Orbits==
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| The inclination is one of the six [[orbital parameters]] describing the shape and orientation of a celestial [[orbit]]. It is the [[angle|angular]] distance of the orbital plane from the [[plane of reference]] (usually the primary's [[equator]] or the [[ecliptic]]), normally stated in [[degree (angle)|degree]]s.<ref>{{cite book
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| | first=Vladimir A. | last=Chobotov | year=2002
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| | title=Orbital Mechanics | pages=28–30;
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| | edition=3rd | publisher=AIAA | isbn=1-56347-537-5 }}</ref>
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| In the [[Solar System]], the inclination of the orbit of a [[planet]] is 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.<ref>{{cite book
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| | author=McBride, Neil; Bland, Philip A.; Gilmour, Iain
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| | title=An Introduction to the Solar System | year=2004
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| | page=248 | publisher=Cambridge University Press
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| | isbn=0-521-54620-6 }}</ref> 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 the Solar System have relatively small inclinations, both in relation to each other and to the Sun's equator. On the other hand, the [[dwarf planet]]s [[Pluto]] and [[Eris (dwarf planet)|Eris]] have inclinations to the [[ecliptic]] of 17 degrees and 44 degrees respectively, and the large [[asteroid]] [[2 Pallas|Pallas]] is inclined at 34 degrees.
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| {{solar system inclinations}}
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| === Natural and artificial satellites ===
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| The inclination of orbits of [[natural satellite|natural]] or [[artificial satellite]]s 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.
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| * an inclination of 0 degrees means the orbiting body orbits the planet in its equatorial plane, in the same direction as the planet rotates;
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| * an inclination greater than −90° and less than 90° is a [[direct motion|prograde orbit]].
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| * an inclination greater than 90° and less than 270° is a [[retrograde motion|retrograde orbit]].
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| * an inclination of exactly 90° is a polar orbit, in which the spacecraft passes over the north and south poles of the planet; and
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| * an inclination of exactly 180° is a retrograde equatorial orbit.
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| For the [[Moon]], measuring its inclination with respect to Earth's equatorial plane leads to a rapidly varying quantity and it makes more sense{{Clarify|date=July 2009}} 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.{{Citation needed|date=November 2011}}
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| ===Exoplanets and multiple star systems===
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| The inclination of [[exoplanet]]s or members of [[Star system|multiple star]]s is the angle of the plane of the orbit relative to the plane perpendicular to the line-of-sight to the object.
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| * An inclination of 0° is a face-on orbit, meaning the plane of its orbit is parallel to the sky.
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| * An inclination of 90° is an edge-on orbit, meaning the plane of its orbit is perpendicular to the sky.
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| Because the [[doppler spectroscopy|radial-velocity method]] more easily finds planets with orbits closer to edge-on, most exoplanets found by this method have inclinations between 45° and 135°, although in most cases the inclination is not known. Consequently, most exoplanets found by radial velocity have true masses no more than 70% greater than their minimum masses. If the orbit is almost face-on, especially for superjovians detected by radial velocity, then those objects may actually be [[brown dwarf]]s or even [[red dwarf]]s. One particular example is [[HD 33636]] B, which has true mass 142 M<sub>J</sub>, corresponding to an M6V star, while its minimum mass was 9.28 M<sub>J</sub>. The inclinations and hence true masses for many exoplanets may eventually be measured by observatories in space, including the [[Gaia mission]], [[Space Interferometry Mission]], and [[James Webb Space Telescope]].{{Citation needed|date=November 2011}}
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| If the orbit is almost edge-on, then the planet can be seen [[transit method|transiting]] its star.
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| == Other meanings ==
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| * 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 or axial inclination, but to avoid ambiguity can be called [[axial tilt]] or '''[[obliquity]]'''.{{Citation needed|date=November 2011}}
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| * In geology, the [[magnetic inclination]] is the angle made by a compass needle with respect to the horizontal surface of the Earth at a given latitude.{{Citation needed|date=November 2011}}
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| ==Calculation==
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| [[image:Orbital inclination from momentum vector.gif|thumb|components of the calculation of the orbital inclination from the momentum vector|right]]
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| In [[astrodynamics]], the inclination <math>i</math> can be computed from the [[orbital momentum vector]] <math>\mathbf{h}\,</math> (or any vector perpendicular to the [[Orbital plane (astronomy)|orbital plane]]) as <math>i=\arccos{h_\mathrm{z}\over\left|\mathbf{h}\right|}</math>, where <math>h_\mathrm{z}</math> is the z-component of <math>\mathbf{h}</math>.
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| Mutual inclination of two orbits may be calculated from their inclinations to another plane using [[Spherical law of cosines|cosine rule for angles]].
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| ==See also==
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| {{Wiktionary|inclination}}
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| * [[Altitude (astronomy)]]
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| * [[Axial tilt]]
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| * [[Azimuth]]
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| * [[Beta Angle]]
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| * [[Kepler orbit]]s
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| * [[Kozai effect]]
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| * [[Orbital inclination change]]
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| ==References==
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| {{More footnotes|date=May 2009}}
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| {{reflist}}
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| {{orbits}}
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| [[Category:Orbits]]
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Stock and Station Agent Boris from Delta, enjoys skeet shooting, health and fitness and fossils. Advocates that you check out Archaeological Site of Leptis Magna.
My web page: Best Use Of Weight Gainer