The eccentricity vector of a Kepler orbit is the vector pointing towards the periapsis having a magnitude equal to the orbit's scalar eccentricity. The magnitude is unitless. For Kepler orbits the eccentricity vector is a constant of motion. Its main use is for almost circular orbits as perturbing (non-Keplarian) forces on an actual orbit will cause the osculating eccentricity vector to change continuously as opposed to the parameters eccentricity and argument of perigee for which eccentricity zero (circular orbit) corresponds to a singularity. See the article Kepler orbit
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Famous quotes containing the word eccentricity:
“Eccentricity has always abounded when and where strength of character has abounded; and the amount of eccentricity in a society has generally been proportional to the amount of genius, mental vigour, and moral courage which it contained.”
—John Stuart Mill (1806–1873)