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The Moon

Moon Moon symbol
Full Moon in the darkness of the night sky. It is patterned with a mix of light-tone regions and darker, irregular blotches, and scattered with varying sizes of impact craters, circles surrounded by out-thrown rays of bright ejecta.
Full Moon as seen from Earth's northern hemisphere
Designations
Adjectives
Orbital characteristics
Perigee 362600 km
(356400370400 km)
Apogee 405400 km
(404000406700 km)
384399 km  (0.00257 AU)
Eccentricity 0.0549
27.321661 d
(27 d 7 h 43 min 11.5 s)
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
Regressing by one revolution in 18.6 years
Progressing by one revolution in 8.85 years
Satellite of Earth
Physical characteristics
Mean radius
1737.1 km  (0.273 Earths)
Equatorial radius
1738.1 km  (0.273 Earths)
Polar radius
1736.0 km  (0.273 Earths)
Flattening 0.0012
Circumference 10921 km  (equatorial)
3.793×107 km2  (0.074 Earths)
Volume 2.1958×1010 km3  (0.020 Earths)
Mass 7.342×1022 kg  (0.012300 Earths)
Mean density
3.344 g/cm3
0.606 × Earth
1.62 m/s2  (0.1654 g)
0.3929±0.0009
2.38 km/s
Sidereal rotation period
27.321661 d  (synchronous)
Equatorial rotation velocity
4.627 m/s
Albedo 0.136
Surface temp. min mean max
Equator 100 K 220 K 390 K
85°N  150 K 230 K
  • −2.5 to −12.9
  • −12.74  (mean full Moon)
29.3 to 34.1 arcminutes
Atmosphere
Surface pressure
  • 10−7Pa (1 picobar)  (day)
  • 10−10 Pa (1 femtobar)   (night)
Composition by volume

The Moon is an astronomical body that orbits planet Earth, being Earth's only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary). Following Jupiter's satellite Io, the Moon is second-densest satellite among those whose densities are known.

The average distance of the Moon from the Earth is 384,400 km (238,900 mi), or 1.28 light-seconds.

The Moon is thought to have formed about 4.51 billion years ago, not long after Earth. There are several hypotheses for its origin; the most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

The Moon is in synchronous rotation with Earth, always showing the same face, with its near side marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters. It is the second-brightest regularly visible celestial object in Earth's sky, after the Sun, as measured by illuminance on Earth's surface. Its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its regular cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art, mythology, and, it is often speculated, the menstrual cycles of the female of the human species.


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Wikipedia

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