Orbital pole: Difference between revisions

[[File:Snapshot of the planetary orbital poles.png|right|300px|thumb|The north orbital poles of the [[Solar System]] planets all lie within [[Draco (constellation)|Draco]]. The central yellow dot in the centre isrepresents the [[Sun]]'s north pole. [[Jupiter]]'s north orbital pole is incolored orange, [[Mercury (planet)|Mercury]] in's pale blue, [[Venus]] in's green, [[Earth]] in's blue, [[Mars]] in's red, [[Saturn]]'s in violetmagenta, [[Uranus]] in's grey, and [[Neptune]] in's lavender. TheThat of the [[dwarf planet]] [[Pluto]] is shown as the dotless cross off in [[Cepheus (constellation)|Cepheus]].]]

An '''orbital pole''' is either endpoint at the ends of the '''orbital normal''', an imaginary [[line runningsegment]] that runs through thea center[[Focus (geometry)|focus]] of an [[orbit]] (of a revolving body) like a [[planet]], [[Natural satellite|moon]] or [[satellite]]) and is [[perpendicular]] (or [[Normal (geometry)|normal]]) to the [[orbital plane]], and. projectedProjected onto the [[celestial sphere]]., Itorbital ispoles are similar in concept to a [[celestial pole]]s, but are based on the [[planet]]body's orbit instead of theits planet's[[celestial rotationequator|equator]].

The [[north]] orbital pole of a celestialrevolving body is defined by the [[right-hand rule]]:. If you curve the fingers of yourthe right hand are curved along the [[retrograde and prograde motion|direction of orbital motion]], with yourthe thumb extended and oriented to be parallel to the orbital [[Axisaxis of rotation|axis]], then the direction yourthe thumb points is defined to be the orbital north.

|[[File:North ecliptic pole.png|320px]]<BR>The Northnorth Eclipticecliptic Polepole is in [[Draco (constellation)|Draco]].

|[[File:South ecliptic pole.png|320px]]<BR>The Southsouth Eclipticecliptic Polepole is in [[Dorado]].

{{as of|1 January 2000}}, the positions of the celestialecliptic poles expressed in [[equatorial coordinate system|equatorial coordinates]], as a consequence of Earth's [[axial tilt]], are the following:

* North: [[right ascension]] {{RA|18|0|0.0}} (exact), [[declination]] {{DEC|+66|33|38.55}}

* South: right ascension {{RA|6|0|0.0}} (exact), declination {{DEC|-66|33|38.55}}

It is impossible anywhere on Earth for either ecliptic pole to be at the [[zenith]] in the [[night sky]]. By definition, the ecliptic poles are located 90° from the [[position of the Sun|Sun's position]]. Therefore, whenever and wherever either ecliptic pole is directly overhead, the Sun must be on the [[horizon]]. The ecliptic poles can contact the zenith only inwithin the [[Arctic Circle|Arctic]] and [[Antarctic Circle|Antarctic]] circles.

[[Category:CelestialAstronomical coordinate systemsystems]]