Periapsis

English

In a 2-body system in which the objects each follow an elliptical orbit around the system's centre of mass, the apsides are: the farthest point, or apoapsis, and the point of closest approach, or periapsis.

Etymology

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Pronunciation

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Noun

1. Template:Lb The point of a body's (elliptical) orbit in a 2-body gravitational system such that the distance between the two bodies (measured from their respective centres of mass) is at its minimum.
   • 1983, Richard O. Fimmel, Laurence Colin, Eric Burgess, Pioneer Venus, NASA SP-461, page 109,

     Figure 5-19. Sun-Venus-Orbiter geometry illustrates how the periapsis moves around the planet during the Venusian sidereal year to sample day and night hemispheres. Because the planet rotates in a retrograde direction, it takes more than one Venusian sidereal year for periapsis to move over all longitudes of the planet (as explained in text).

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   • 2004, R. S. Saunders, et al., Mars Odyssey Mission, C. T. Russell (editor), 2001 Mars Odyssey, Kluwer Academic Publishers, page 34,

     The main aerobraking phase began once the point of the spacecraft's periapsis had been lowered to within 110 km above the Martian surface.

2. The minimum distance between the two bodies in such a system.

Usage notes

• In the case of some particular celestial bodies, specialized terms are used. See Related terms, below, for examples.

Synonyms

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Antonyms

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Hypernyms

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Derived terms

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Translations

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Further reading

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Finnish

Etymology

Template:Internationalism (see Template:Cog).

Noun

1. Template:Lb periapsis