Orbiting body

In astrodynamics, an orbiting body is any physical body that orbits a more massive one, called the primary body. The orbiting body is properly referred to as the secondary body (${\displaystyle m_{2}}$),[1] which is less massive than the primary body (${\displaystyle m_{1}}$).

Thus, ${\displaystyle m_{2}<m_{1}}$ or ${\displaystyle m_{1}>m_{2}}$.

Under standard assumptions in astrodynamics, the barycenter of the two bodies is a focus of both orbits.

An orbiting body may be a spacecraft (i.e. an artificial satellite) or a natural satellite, such as a planet, dwarf planet, moon, moonlet, asteroid, or comet.

A system of two orbiting bodies is modeled by the Two-Body Problem and a system of three orbiting bodies is modeled by the Three-Body Problem. These problems can be generalized to an N-body problem. While there are a few analytical solutions to the n-body problem, it can be reduced to a 2-body system if the secondary body stays out of other bodies Sphere of Influence and remains in the primary bodies sphere of influence [2].

See also

• Barycenter
• Double planet
• Primary (astronomy)
• Satellite
• Two-body problem
• Three-body problem
• N-body problem

References

1. "Dictionary of Technical Terms for Aerospace Use". NASA. Retrieved 2010-05-11.
2. Curtis, Howard D. (2009). Orbital Mechanics for Engineering Students, 2e. New York: Elsevier. ISBN 978-0-12-374778-5.