semimajor axis
noun
semi·ma·jor axis
ˌse-mē-ˈmā-jər- 
ˌse-ˌmī-,
-mi-
: one half of the major axis of an ellipse (such as that formed by the orbit of a planet)
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The uncertainty in its semimajor axis (the radius of its orbit at its two most separated points) is just six meters out of a total length of 168,505,699.049 kilometers.
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Dante S. Lauretta, Scientific American, 1 Aug. 2016
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Dante S. Lauretta, Scientific American, 1 Aug. 2016
Cite this Entry
“Semimajor axis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/semimajor%20axis. Accessed 12 May. 2025.
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