Sphere of influence (astrodynamics)

<p>A sphere of influence (SOI) in <a href="/facts/Astrodynamics/oB3tqNG9">astrodynamics</a> and <a href="/facts/Astronomy/0ArJVM1p">astronomy</a> is the <a href="/facts/Spheroid/GJyyLxQ7">oblate spheroid</a>-shaped region where a particular <a href="/facts/Celestial_body/BCHLa0Q2">celestial body</a> exerts the main <a href="/facts/Gravity/bqAN7DdQ">gravitational</a> influence on an <a href="/facts/Orbit/nD2TPySG">orbiting</a> object. This is usually used to describe the areas in the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a> where <a href="/facts/Planets/rbPjE6Bx">planets</a> dominate the orbits of surrounding objects such as <a href="/facts/Natural_satellite/AE4KQKbq">moons</a>, despite the presence of the much more massive but distant <a href="/facts/Sun/CadPCVHh">Sun</a>. 
</p><p>In the <a href="/facts/Patched_conic_approximation/F41LIEWg">patched conic approximation</a>, used in estimating the trajectories of bodies moving between the neighbourhoods of different bodies using a two-body approximation, ellipses and hyperbolae, the SOI is taken as the boundary where the trajectory switches which mass field it is influenced by. It is not to be confused with the sphere of activity which extends well beyond the sphere of influence.
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Sphere of influence (astrodynamics) open-in-new

Sphere of influence (astrodynamics)