Back Monan hwyrft ANG مدار القمر Arabic Арбіта Месяца Byelorussian Òrbita de la Lluna Catalan Mondbahn German Τροχιά της Σελήνης Greek Orbit of the Moon English Órbita de la Luna Spanish Ilargiaren orbita Basque مدار ماه Persian
 Diagram of the Moon's orbit with respect to the Earth. While angles and relative sizes are to scale, distances are not. | |
| Semi-major axis[a] | 384,748 km (239,071 mi)[1] |
|---|---|
| Mean distance[b] | 385,000 km (239,000 mi)[2] |
| Inverse sine parallax[c] | 384,400 km (238,900 mi) |
| Perigee | 363,228.9 km (225,700.0 mi), avg. (356400–370400 km) |
| Apogee | 405,400 km (251,900 mi), avg. (404000–406700 km) |
| Mean eccentricity | 0.0549006 (0.026–0.077)[3] |
| Mean obliquity | 6.687°[5] |
| Mean inclination | |
| of orbit to ecliptic | 5.15° (4.99–5.30)[3] |
| of lunar equator to ecliptic | 1.543° |
| Period of | |
| orbit around Earth (sidereal) | 27.322 days |
| orbit around Earth (synodic) | 29.530 days |
| precession of nodes | 18.5996 years |
| precession of line of apsides | 8.8504 years |
The Moon takes 27.3 days (3.9 weeks) to orbit around the Earth. One side of the Moon faces the Earth at all times, so the moon is tidally locked to Earth.
The phases of the Moon come from the position of the Moon relative to the Earth and Sun. If the Moon and Sun are on opposite sides of the Earth, there is a full moon. If they are on the same side of Earth, there is a new moon.
The Moon makes one circle around Earth, called the sidereal month, in 27.3 days. But in this time, the Earth continues to move forward, so the Moon will be in a different place relative to the Sun, and the phase of the Moon will be different. To reach the same phase, the Moon must travel a bit farther. The time for the Moon to reach the same phase, called the synodic month, is 29.5 days.
- ↑ M. Chapront-Touzé; J. Chapront (1983). "The lunar ephemeris ELP-2000". Astronomy & Astrophysics. 124: 54. Bibcode:1983A&A...124...50C.
- ↑ M. Chapront-Touzé; J. Chapront (1988). "ELP2000-85: a semi-analytical lunar ephemeris adequate for historical times". Astronomy & Astrophysics. 190: 351. Bibcode:1988A&A...190..342C.
- ↑ 3.0 3.1 3.2 Meeus, Jean (1997), Mathematical Astronomy Morsels, Richmond, VA: Willmann-Bell, pp. 11–12, 22–23, ISBN 0-943396-51-4
- ↑ Seidelmann, P. Kenneth, ed. (1992), Explanatory Supplement to the Astronomical Almanac, University Science Books, pp. 696, 701, ISBN 0-935702-68-7
- ↑ Lang, Kenneth R. (2011), The Cambridge Guide to the Solar System, 2nd ed., Cambridge University Press.
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