Transit of Earth from Neptune
A [[Astronomical transit|transit]] '''of''' [[Earth]] '''across the''' [[Sun]] '''as seen from''' [[Neptune]] takes place when the planet Earth passes directly between the Sun and Neptune, obscuring a small part of the Sun's disc for an observer on Neptune. During a transit, Earth can be seen from Neptune as a small black disc moving across the face of the Sun.
Naturally, no one has ever seen a transit of Earth from Neptune, nor is this likely to happen in the foreseeable future. Nevertheless, the last such event took place on [[August 11]], [[2006]] and the next will be a grazing transit on [[January 23]], [[2081]]. The next central transit takes place on [[January 25]], [[2082]].
A transit could be observed from the surface of one of Neptune's moons rather than from Neptune itself. The times and circumstances of the transits would naturally be slightly different.
The Earth-Neptune [[synodic period]] is 367.486 days. It can be calculated using the formula 1/(1/P-1/Q), where P is the [[sidereal orbital period]] of Earth (365.25636 days) and Q is the [[orbital period]] of Neptune (60,190 days).
Transits of Earth from Neptune are empirically observed to occur in clusters, with two such clusters every 80 years or so. These clusters occur whenever Neptune is closest to the ecliptic because the ecliptic is the plane of Earth's orbit and planetary transits only occur when planets are aligned.
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! Transits 2001-2100
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| [[July 30]], [[2001]]
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| [[August 2]], [[2002]]
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| [[August 4]], [[2003]]
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| [[August 6]], [[2004]]
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| [[August 8]], [[2005]]
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| [[August 11]], [[2006]]
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| [[January 23]], [[2081]] grazer
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| [[January 25]], [[2082]]
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| [[January 28]], [[2083]]
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| [[January 30]], [[2084]]
|-
| [[February 1]], [[2085]]
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| [[February 3]], [[2086]]
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| [[February 6]], [[2087]]
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| [[February 8]], [[2088]]
|}
==Transit visibility table==
==See also==
* [[Astronomical transit]]
{{transit visibility table}}
==External links==
* [http://ssd.jpl.nasa.gov/?HORIZONS JPL Horizons]
{{Neptune}}
[[Category:Astronomical transits]]
[[Category:Neptune]]
[[ko:해왕성에서 본 지구 일면통과]]