Apocentre

Part of speech: noun

Definitions

1. The point in an orbit that is farthest from the center of attraction or focus of the orbiting body
2. The location in an elliptical path where the distance to the central mass is at its maximum
3. A celestial term denoting the most distant point from the central force in an orbital trajectory

Etymology: "Apocentre" is a technical coinage built from two parts that each carry long histories. The first, "apo-", comes from Ancient Greek "apó", meaning "away from" or "off", and it reached English as a prefix in scientific vocabulary. The second, "centre", goes back through Latin "centrum" to Ancient Greek "kéntron", a word for a sharp point, such as the point of a goad or compass, before it came to mean the middle of a circle. Put together, the pieces describe a body that moves "away from the centre." In astronomy the centre in question is the body being orbited, so the apocentre is the point in an orbit furthest from that centre. Its opposite, the pericentre, marks the nearest approach. The pairing reflects a practical need of celestial mechanics, where orbits were described by their extremes rather than by a single name for the whole path.

Synonyms: apogee