Knowra Orbital eccentricity Orbital eccentricity Orbital eccentricity is a dimensionless parameter describing an orbit’s shape, from a circle at zero through increasingly elongated ellipses to parabolic and hyperbolic paths.
Keplerian orbit : An idealized orbit governed by Newtonian gravity between two point masses. Its conic-section paths are classified by eccentricity.
Ellipse : A closed curve whose points have a constant sum of distances from two foci. Bound Keplerian orbits are ellipses, with eccentricity measuring their departure from circularity.
Earth's orbit : The path Earth follows around the Sun, approximated closely by an ellipse. Its small but nonzero eccentricity produces modest annual changes in Earth–Sun distance.
Orbital inclination : The angle between an orbit's plane and a chosen reference plane. Inclination describes orbital orientation, while eccentricity describes orbital shape.
Conic section : A curve formed by intersecting a plane with a cone, including circles, ellipses, parabolas, and hyperbolas. Orbital eccentricity distinguishes the shapes available to an ideal gravitational trajectory.
Focus (geometry) : A fixed point used to define a conic section; an ellipse has two foci. A central gravitating body lies at one focus of an ideal elliptical orbit.
Milankovitch cycles : Long-term variations in Earth's orbit and rotation that influence the distribution of incoming sunlight. Changes in Earth's orbital eccentricity contribute to climate rhythms over tens to hundreds of thousands of years.
Orbital period : The time an orbiting body takes to complete one revolution. Period measures orbital timing, not the conic's departure from a circle.
Semimajor axis : Half the longest diameter of an ellipse, or a signed length parameter for other conic orbits. Together with eccentricity, it sets an ellipse’s dimensions and focus distance.
Semi-latus rectum : Half the length of a conic’s chord through a focus and perpendicular to its axis. It combines with eccentricity to express orbital radius as a function of true anomaly.
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