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Orbit ○꠹｜Definition｜1st｜20251119205401-00-⌔
Orbit
In celestial mechanics, an orbit is the curved trajectory of an object1 under the influence of an attracting force. Alternatively, it is known as an orbital revolution, because it is a rotation around an axis external to the moving body. Examples for orbits include the trajectory of a planet around a star, a natural satellite around a planet, or an 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 orbits, with the center of mass being orbited at a focal point of the ellipse,2 as described by Kepler’s laws of planetary motion.
Planets revolve around a star, a natural satellite around a planet, or an artificial satellite around an object or position in space such as a planet, moon, asteroid, or Lagrange point.
For most situations, orbital motion is adequately approximated by Newtonian mechanics, which explains gravity as a force obeying an inverse-square law.3 However, Albert Einstein’s general theory of relativity, which accounts for gravity as due to curvature of spacetime, with orbits following geodesics, provides a more accurate calculation and understanding of the exact mechanics of orbital motion.
Printed 2026-06-28.
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Link to original Footnotes
“orbit (astronomy)”. Encyclopædia Britannica (Online ed.). Archived from the original on 5 May 2015. Retrieved 28 July 2008. ↩
“The Space Place:: What’s a Barycenter”. NASA. Archived from the original on 8 January 2013. Retrieved 26 November 2012. ↩
Kuhn, Thomas S. (1985) [1957]. The Copernican Revolution. Harvard University Press. pp. 238, 246–252. ISBN 978-0-674-17103-9. ↩
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