|—n , pl -lies|
|2.||deviation from the normal or usual order, type, etc; irregularity|
|a. Also called: true anomaly the angle between a planet, the sun, and the previous perihelion of the planet|
|b. Also called: eccentric anomaly the angle between the periapsis of a particular point on a circle round the orbit as seen from the centre of the orbit. This point is obtained by producing a perpendicular to the major axis of the ellipse through the orbiting body until it reaches the circumference of the circle|
|c. Also called: mean anomaly the angle between the periapsis of an orbit and the position of an imaginary body orbiting at a constant angular speed and in the same period as the real orbiting body|
|a. Also called: gravity anomaly a deviation from the normal value of gravity at the earth's surface, caused by density differences at depth, for example those caused by a buried mineral body|
|b. Also called: magnetic anomaly a magnetic field, for example one produced by a buried mineral body, that deviates from an expected or standard value, usually that of the earth's magnetic field|
anomaly a·nom·a·ly (ə-nŏm'ə-lē)
A deviation from the average or norm.
in astronomy, originally the nonuniform (anomalous) apparent motions of the planets. In present usage, three kinds of anomaly are distinguished to describe the position in the orbit of a planet, a satellite, or a star (in a binary system) around the centre of mass. The following text relates to the orbit of a planet. True anomaly is the angle, V, between lines drawn from the centre of mass (near the centre of the Sun, S), to a planet P, and to the perihelion point B, where the planet comes closest to the Sun. The mean anomaly is the angle between lines drawn from the Sun to the perihelion B and to a point (not shown) moving in the orbit at a uniform rate corresponding to the period of revolution of the planet. The eccentric anomaly is the angle E, between the perihelion B, the centre of the ellipse at C, and the point P', which is located by drawing a perpendicular to AB passing through the planet and intersecting a circle of diameter AB.
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