Apsis

: This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms). In architecture, apsis is a synonym for apse; Apogee is also the name of a video game publisher.

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In astronomy, an apsis (plural apsides "ap-si-deez") is the point of greatest or least distance of the elliptical orbit of a celestial body from its center of attraction (the center of mass of the system).

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The point of closest approach is called the periapsis or pericentre and the point of farthest approach is the apoapsis (Greek απο, from), apocentre or apapsis (the latter term, although etymologically more correct, is much less used). A straight line drawn through the periapsis and apoapsis is the line of apsides. This is the major axis of the ellipse, the line through the longest part of the ellipse.

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Related terms are used to identify the body being orbited. The most common are perigee and apogee, referring to Earth orbits, and perihelion and aphelion, referring to orbits around the Sun (Greek ἡλιος).

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Apse: This article is about an architectural feature; for the astronomical term see apsis....

Apogee: REDIRECT apsis...

Video game publisher: Video game publishers are companies that publish video games that they have either developed internally or have had developed by a video game developer. Most video game publishers also produce and publish computer games, but the term "video game publisher" is often used generically to refer to compa...