Orbiting body

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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 ($m\_2$),{{cite web |title=Dictionary of Technical Terms for Aerospace Use |url=http://er.jsc.nasa.gov/SEH/s.html |publisher=NASA |access-date=2010-05-11}} which is less massive than the primary body ($m\_1$).

Thus, or $m\_1\; >\; m\_2$.

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 body's sphere of influence.{{cite book|author=Curtis, Howard D.|title=Orbital Mechanics for Engineering Students, 2e|publisher=Elsevier|location=New York|date=2009|isbn=978-0-12-374778-5}}