An apsis (plural apsides // AP-sih-deez, from Greek "orbit") is the farthest or nearest point in the orbit of a planetary body about its primary body. The apsides of Earth's orbit of the Sun are two: the aphelion, where Earth is farthest from the sun, and the perihelion, where it is nearest. "Apsides" can also refer to the distance of the extreme range of an object orbiting a host body.
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*The line of apsides is the line connecting positions 1 and 2.
*The table names the (two) apsides of a planetary body (X, "orbiter") orbiting the host body indicated:
|(1) farthest||(X) orbiter||(3) host||(2) nearest|
For example, the Moon's two apsides are the farthest point, apogee, and the nearest point, perigee, of its orbit around the host Earth. The Earth's two apsides are the farthest point, aphelion, and the nearest point, perihelion, of its orbit around the host Sun. The terms aphelion and perihelion apply in the same way to the orbits of Jupiter and the other planets, the comets, and the asteroids of the Solar System.
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