Global InformationMoon information
 Near side of the Moon, lunar north pole at top | |||||||||||||
| Designations | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Designation | Earth I | ||||||||||||
Alternative names |
| ||||||||||||
| Adjectives |
| ||||||||||||
| Symbol |  or  | ||||||||||||
| Orbital characteristics | |||||||||||||
| Epoch J2000 | |||||||||||||
| Perigee | 362600 km (356400–370400 km) | ||||||||||||
| Apogee | 405400 km (404000–406700 km) | ||||||||||||
Semi-major axis | 384399 km (1.28 ls, 0.00257 AU)[1] | ||||||||||||
| Eccentricity | 0.0549[1] | ||||||||||||
Orbital period (sidereal) | 27.321661 d (27 d 7 h 43 min 11.5 s[1]) | ||||||||||||
Orbital period (synodic) | 29.530589 d (29 d 12 h 44 min 2.9 s) | ||||||||||||
Average orbital speed | 1.022 km/s | ||||||||||||
| Inclination | 5.145° to the ecliptic[2][a] | ||||||||||||
Longitude of ascending node | Regressing by one revolution in 18.61 years | ||||||||||||
Argument of perigee | Progressing by one revolution in 8.85 years | ||||||||||||
| Satellite of | Earth[b][3] | ||||||||||||
| Physical characteristics | |||||||||||||
Mean radius | 1737.4 km (0.2727 of Earth's)[1][4][5] | ||||||||||||
Equatorial radius | 1738.1 km (0.2725 of Earth's)[4] | ||||||||||||
Polar radius | 1736.0 km (0.2731 of Earth's)[4] | ||||||||||||
| Flattening | 0.0012[4] | ||||||||||||
| Circumference | 10921 km (equatorial) | ||||||||||||
Surface area | 3.793×107 km2 (0.074 of Earth's) | ||||||||||||
| Volume | 2.1958×1010 km3 (0.02 of Earth's)[4] | ||||||||||||
| Mass | 7.342×1022 kg (0.0123 of Earth's)[1][4][6] | ||||||||||||
Mean density | 3.344 g/cm3[1][4] 0.606 × Earth | ||||||||||||
Surface gravity | 1.622 m/s2 (0.1654 g; 5.318 ft/s2)[4] | ||||||||||||
Moment of inertia factor | 0.3929±0.0009[7] | ||||||||||||
Escape velocity | 2.38 km/s (8600 km/h; 5300 mph) | ||||||||||||
Synodic rotation period | 29.530589 d (29 d 12 h 44 min 2.9 s; synodic; solar day) (spin-orbit locked) | ||||||||||||
Sidereal rotation period | 27.321661 d (spin-orbit locked) | ||||||||||||
Equatorial rotation velocity | 4.627 m/s | ||||||||||||
Axial tilt |
| ||||||||||||
North pole right ascension |
| ||||||||||||
North pole declination | 65.64°[10] | ||||||||||||
| Albedo | 0.136[11] | ||||||||||||
| |||||||||||||
| Surface absorbed dose rate | 13.2 μGy/h (during lunar daytime)[14] | ||||||||||||
| Surface equivalent dose rate | 57.0 μSv/h (during lunar daytime)[14] | ||||||||||||
Apparent magnitude |
| ||||||||||||
Absolute magnitude (H) | 0.2[15] | ||||||||||||
Angular diameter | 29.3 to 34.1 arcminutes[4][d] | ||||||||||||
| Atmosphere[16] | |||||||||||||
Surface pressure |
| ||||||||||||
| Composition by volume |
| ||||||||||||
The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Over time Earth's gravity has caused tidal locking, causing the same side of the Moon to always face Earth. Because of this, the lunar day and the lunar month are the same length, at 29.5 Earth days. The Moon's gravitational pull – and to a lesser extent, the Sun's – are the main drivers of Earth's tides.
In geophysical terms the Moon is a planetary-mass object or satellite planet. Its mass is 1.2% that of the Earth, and its diameter is 3,474 km (2,159 mi), roughly one-quarter of Earth's (about as wide as Australia.[17]) Within the Solar System, it is the largest and most massive satellite in relation to its parent planet, the fifth largest and most massive moon overall, and larger and more massive than all known dwarf planets.[18] Its surface gravity is about one sixth of Earth's, about half of that of Mars, and the second highest among all Solar System moons, after Jupiter's moon Io. The body of the Moon is differentiated and terrestrial, with no significant hydrosphere, atmosphere, or magnetic field. It formed 4.51 billion years ago, not long after Earth's formation, out of the debris from a giant impact between Earth and a hypothesized Mars-sized body called Theia.
The lunar surface is covered in lunar dust and marked by mountains, impact craters, their ejecta, ray-like streaks and, mostly on the near side of the Moon, by dark maria ("seas"), which are plains of cooled magma. These maria were formed when molten lava flowed into ancient impact basins. The Moon is, except when passing through Earth's shadow during a lunar eclipse, always illuminated by the Sun, but from Earth the visible illumination shifts during its orbit, producing the lunar phases.[19] The Moon is the brightest celestial object in Earth's night sky. This is mainly due to its large angular diameter, while the reflectance of the lunar surface is comparable to that of asphalt. The apparent size is nearly the same as that of the Sun, allowing it to cover the Sun completely during a total solar eclipse. From Earth about 59% of the lunar surface is visible over time due to cyclical shifts in perspective (libration), making parts of the far side of the Moon visible.
For humans the Moon has been an important source of inspiration and knowledge, having been crucial to cosmography, mythology, religion, art, time keeping, natural science, and spaceflight. On September 13, 1959, the first human-made object to reach an extraterrestrial body arrived on the Moon, the Soviet Union's Luna 2 impactor. In 1966, the Moon became the first extraterrestrial body where soft landings and orbital insertions were achieved. On July 20, 1969, humans for the first time landed on the Moon and any extraterrestrial body, at Mare Tranquillitatis with the lander Eagle of the United States' Apollo 11 mission. Five more crews were sent between then and 1972, each with two men landing on the surface. The longest stay was 75 hours by the Apollo 17 crew. Since then, exploration of the Moon has continued robotically with crewed missions being planned to return beginning in the late 2020s.
- ^ a b c d e f g Cite error: The named reference
W06was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
Lang2011was invoked but never defined (see the help page). - ^ Cite error: The named reference
Morais2002was invoked but never defined (see the help page). - ^ a b c d e f g h i j Cite error: The named reference
NSSDCwas invoked but never defined (see the help page). - ^ Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Lemoine, Frank G. (January 1, 1997). "Topography of the Moon from the Clementine lidar". Journal of Geophysical Research. 102 (E1): 1601. Bibcode:1997JGR...102.1591S. doi:10.1029/96JE02940. hdl:2060/19980018849. S2CID 17475023.
- ^ Terry, Paul (2013). Top 10 of Everything. Octopus Publishing Group Ltd. p. 226. ISBN 978-0-600-62887-3.
- ^ Cite error: The named reference
Williams1996was invoked but never defined (see the help page). - ^ Cite error: The named reference
SolarViewswas invoked but never defined (see the help page). - ^ Makemson, Maud W. (1971). "Determination of selenographic positions". The Moon. 2 (3): 293–308. Bibcode:1971Moon....2..293M. doi:10.1007/BF00561882. S2CID 119603394.
- ^ a b Archinal, Brent A.; A'Hearn, Michael F.; Bowell, Edward G.; Conrad, Albert R.; Consolmagno, Guy J.; Courtin, Régis; Fukushima, Toshio; Hestroffer, Daniel; Hilton, James L.; Krasinsky, George A.; Neumann, Gregory A.; Oberst, Jürgen; Seidelmann, P. Kenneth; Stooke, Philip J.; Tholen, David J.; Thomas, Paul C.; Williams, Iwan P. (2010). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009" (PDF). Celestial Mechanics and Dynamical Astronomy. 109 (2): 101–135. Bibcode:2011CeMDA.109..101A. doi:10.1007/s10569-010-9320-4. S2CID 189842666. Archived from the original (PDF) on March 4, 2016. Retrieved September 24, 2018. also available "via usgs.gov" (PDF). Archived (PDF) from the original on April 27, 2019. Retrieved September 26, 2018.
- ^ Cite error: The named reference
Saariwas invoked but never defined (see the help page). - ^ a b Bugby, D. C.; Farmer, J. T.; O’Connor, B. F.; Wirzburger, M. J.; C. J. Stouffer, E. D. Abel (January 2010). Two-Phase Thermal Switching System for a Small, Extended Duration Lunar Surface Science Platform. AIP Conference Proceedings. Vol. 1208. pp. 76–83. Bibcode:2010AIPC.1208...76B. doi:10.1063/1.3326291. hdl:2060/20100009810.
- ^ Cite error: The named reference
Vasavada1999was invoked but never defined (see the help page). - ^ a b Zhang S, Wimmer-Schweingruber RF, Yu J, Wang C, Fu Q, Zou Y, et al. (2020). "First measurements of the radiation dose on the lunar surface". Science Advances. 6 (39). Bibcode:2020SciA....6.1334Z. doi:10.1126/sciadv.aaz1334. PMC 7518862. PMID 32978156.
We measured an average total absorbed dose rate in silicon of 13.2 ± 1 μGy/hour ... LND measured an average dose equivalent of 1369 μSv/day on the surface of the Moon
- ^ "Encyclopedia - the brightest bodies". IMCCE. Archived from the original on March 21, 2023. Retrieved June 1, 2023.
- ^ Cite error: The named reference
L06was invoked but never defined (see the help page). - ^ Cite error: The named reference
Australiawas invoked but never defined (see the help page). - ^ Cite error: The named reference
Metzger2021was invoked but never defined (see the help page). - ^ "Is the 'full moon' merely a fallacy?". NBC News. February 28, 2004. Archived from the original on June 1, 2023. Retrieved May 30, 2023.
Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).