Editing Orbit (section)

{{Short description|Curved path of an object around a point}}
{{About|orbits in celestial mechanics, due to gravity}}
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{{Use dmy dates|date=September 2019}}
[[File:Animation of C-2018 Y1 orbit 1600-2500.gif|upright=1.5|thumb|An animation showing a low [[Orbital eccentricity|eccentricity]] orbit (near-circle, in red), and a high eccentricity orbit (ellipse, in purple)]]

In [[celestial mechanics]], an '''orbit''' (also known as '''orbital revolution''') is the curved [[trajectory]] of an [[physical body|object]]<ref>{{Cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/431123/orbit |title=orbit (astronomy) |encyclopedia=Encyclopædia Britannica |edition=Online |access-date=28 July 2008 |archive-date=5 May 2015 |archive-url=https://web.archive.org/web/20150505012919/https://www.britannica.com/EBchecked/topic/431123/orbit |url-status=live }}</ref> such as the trajectory of a [[planet]] around a star, or of a [[natural satellite]] around a planet, or of an [[satellite|artificial satellite]] around an object or position in space such as a planet, moon, asteroid, or [[Lagrange point]]. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow [[elliptic orbit]]s, with the [[barycenter|center of mass]] being orbited at a focal point of the ellipse,<ref>{{Cite web |url=http://spaceplace.nasa.gov/barycenter/ |title=The Space Place :: What's a Barycenter |access-date=26 November 2012 |archive-date=8 January 2013 |archive-url=https://web.archive.org/web/20130108073405/http://spaceplace.nasa.gov/barycenter/ |publisher=NASA |url-status=live }}</ref> as described by [[Kepler's laws of planetary motion]].

For most situations, orbital motion is adequately approximated by [[Newtonian mechanics]], which explains [[Newton's law of universal gravitation|gravity]] as a force obeying an [[inverse-square law]].<ref>Kuhn, ''The Copernican Revolution'', pp. 238, 246–252</ref> However, [[Albert Einstein]]'s [[general theory of relativity]], which accounts for gravity as due to curvature of [[spacetime]], with orbits following [[geodesic]]s, provides a more accurate calculation and understanding of the exact mechanics of orbital motion.