Orbital eccentricity

<p>In <a href="/facts/Astrodynamics/oB3tqNG9">astrodynamics</a>, the orbital eccentricity of an <a href="/facts/Astronomical_object/BCHLa0Q2">astronomical object</a> is a <a href="/facts/Dimensionless_quantity/TINrpQIq">dimensionless parameter</a> that determines the amount by which its <a href="/facts/Orbit/nD2TPySG">orbit</a> around another body deviates from a perfect <a href="/facts/Circle/9fy5ggKn">circle</a>. A value of 0 is a <a href="/facts/Circular_orbit/sSFMzmBv">circular orbit</a>, values between 0 and 1 form an <a href="/facts/Elliptic_orbit/SfuXuATN">elliptic orbit</a>, 1 is a <a href="/facts/Parabola/Cweo3wgw">parabolic</a> <a href="/facts/Escape_orbit/vDNtF83E">escape orbit</a> (or capture orbit), and greater than 1 is a <a href="/facts/Hyperbola/6R6ER0mY">hyperbola</a>. The term derives its name from the parameters of <a href="/facts/Conic_section/teqgLptX">conic sections</a>, as every <a href="/facts/Kepler_orbit/XvdtxmKl">Kepler orbit</a> is a conic section. It is normally used for the isolated <a href="/facts/Two-body_problem/YCG4geSH">two-body problem</a>, but extensions exist for objects following a <a href="/facts/Klemperer_rosette/1gsrQDg5">rosette</a> orbit through the Galaxy.
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Orbital eccentricity open-in-new

Orbital eccentricity