Periastrons

Part of speech: noun

Definitions

1. A term denoting the closest point of approach in an orbit involving two celestial bodies
2. Referring to the position in an orbit where one object is nearest to another, such as a planet to its star
3. Describing the part of an orbit indicating maximum proximity between satellite-like objects or celestial entities

Etymology: "Periastrons" is simply the plural of "periastron," a term for the point in an orbit where two bodies orbiting each other come closest together. The singular is built from two Ancient Greek elements: "perí," meaning "around" or "near," and "ástron," meaning "star." Together they describe a point in the path of one star or planet around another, where the pair is nearest. The compound follows a pattern familiar from astronomy, where Greek roots were combined to name newly understood phenomena. The Greek "perí" also appears in "perigee," the closest approach of the Moon or a satellite to Earth, and "perihelion," the closest approach of a planet to the Sun, which share the same structure but use "gê" (earth) and "hêlios" (sun) in place of "ástron." Each term marks the nearest point of an orbit around a different central body.