What is perihilum?

Perihilum is a term used in astronomy to refer to the point in an orbit where a celestial body is closest to its primary focus, typically a star or planet. It is derived from the Greek Words "peri," meaning around, and "hilum," meaning a small area or spot. In the context of planetary orbits, perihilum is analogous to periapsis, which describes the closest approach of an object in orbit to its central body, while "aphelion" refers to the furthest point in the orbit.