semimajor axis

American  

[sem-ee-mey-jer, sem-ahy-, sem-ee-, sem-ahy-] / ˈsɛm iˈmeɪ dʒər, ˈsɛm aɪ-, ˌsɛm i-, ˌsɛm aɪ- /

noun

1. Geometry. one half the major axis of an ellipse.

2. Astronomy. one half the major axis of the ellipse that one celestial body describes around another, as a planet around the sun or a satellite around a planet, equivalent to the mean distance between the two bodies.

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Etymology

Origin of semimajor axis

First recorded in 1925–30; semi- + major

Example Sentences

See Examples For:

semimajor axis

Venus’ orbital period is 0.62 year, and its semimajor axis is 0.72 AU.

From Textbooks ● Oct. 13, 2016

Also, recall that a planet’s semimajor axis, a, is equal to its average distance from the Sun.

From Textbooks ● Oct. 13, 2016

Half this distance—that is, the distance from the center of the ellipse to one end—is the semimajor axis, which is usually used to specify the size of the ellipse.

From Textbooks ● Oct. 13, 2016

In a circle, the semimajor axis would be the radius.

From Textbooks ● Oct. 13, 2016

The semimajor axis of Mercury’s orbit—that is, the planet’s average distance from the Sun—is 58 million kilometers, or 0.39 AU.

From Textbooks ● Oct. 13, 2016