anomalistic year

anomalistic year , time required for the earth to go from the perihelion point once around the sun and back to the perihelion point. It is 365 days, 6 hr, 13 min, 53.0 sec of mean solar time (see solar time ). The anomalistic year is longer than the sidereal year and the tropical year because of the eastward motion of the line of apsides (see apsis ), which is caused by the slow rotation of the earth's orbit as a whole.

anomalistic year The interval of time between successive passages of the Earth through the perihelion of its orbit, equal to 365.2596 days. Due to perturbations by the other planets, the Earth's orbit is not a fixed ellipse but one that is slowly advancing. As a result the anomalistic year is about 5 min longer than the Earth's orbital period (the sidereal year).

anomalistic month The mean interval of time between successive passages of the Moon through its closest point to Earth (its perigee), equal to 27.55464 days. The Moon's orbit is not fixed in space but can be regarded as a slowly rotating ellipse, the rotation due principally to perturbation by the Sun. Hence the perigee point advances slowly around the orbit, completing one circuit in 8.85 years. As a consequence, the anomalistic month is about 5.5 hours longer than the sidereal month.