Description: Aphelion is the point along an orbit around the Sun where the orbiting body is farthest from the Sun. Objects orbiting the Sun and not affected by any other object have orbits with an elliptical shape with the Sun at one of the foci of this ellipse. Mathematically, aphelion marks one end of the major axis of the ellipse. In this word "ap" denotes farthest point and "helion" denotes the Sun. Accordingly, this term may only be used when the central body is the Sun. When the central body is a star that is not the Sun, the term is either "apastron" or "apoastron"; when the central body being orbited is the Earth the term is "apogee". The general term regardless of the central body is "apoapsis".

Related Terms:

• Ellipse
• Orbit
• Perihelion
• Solar System

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".