------------------------------------------------- EARTHS SATELLITE -- THE MOON ------------------------------------------------- ------------------------------------- A SCIENTIFIC OVERVIEW ------------------------------------- Orbital characteristics Perigee 362600 km (356400–370400 km) - Apogee 405400 km (404000–406700 km) - Semi-major axis 384399 km (0.00257 AU) - Eccentricity 0.0549 - Orbital period 27.321582 d 27d 7h 43.1min - Synodic period 29.530589 d (29d 12h 44min 2.9s) - Average orbital speed 1.022 km/s - Inclination 5.145° to the ecliptic - Longitude of ascending node regressing by one revolution in 18.6 years - Argument of perigee progressing by one revolution in 8.85 years - Satellite of Earth - - Physical characteristics - Mean radius 1737.10 km (0.273 Earths) - Equatorial radius 1738.14 km (0.273 Earths) - Polar radius 1735.97 km (0.273 Earths) - Flattening 0.00125 - Circumference 10921 km (equatorial) - Surface area 3.793×107 km2 (0.074 Earths) - Volume 2.1958×1010 km3 (0.020 Earths) - Mass 7.3477×1022 kg (0.012300 Earths) - Mean density 3.3464 g/cm3 - Surface gravity 1.622 m/s2 (0.1654 g) - Moment of inertia factor 0.3929±0.0009 - Escape velocity 2.38 km/s - Sidereal rotation period 27.321582 d (synchronous) - Equatorial rotation velocity 4.627 m/s - Axial tilt 1.5424° to ecliptic 6.687° to orbit plane Albedo 0.136[5] - --Equator 100 K 220 K 390 K 85°N 70 K 130 K 230 K - -- Apparent magnitude −2.5 to −12.9[b] −12.74 (mean full moon) - -- Angular diameter 29.3 to 34.1 arcminutes - Composition Ar · He · Na · K · H · Rn - ------------------------------- GENERAL OVERVIEW -------------------------------- - The Moon (Latin: Luna) is the Earths only natural satellite. Although not the largest natural satellite in the Solar System, it is the largest relative to the size of the object it orbits (its primary) and, after Jupiters satellite Io, it is the second most dense satellite among those whose densities are known. - The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. It is the most luminous object in the sky after the Sun. - Although it appears a very bright white, its surface is actually dark, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art, and mythology. - The Moons gravitational influence produces the ocean tides and the slight lengthening of the day. The Moons current orbital distance is about thirty times the diameter of Earth, causing it to have an apparent size in the sky almost the same as that of the Sun. This allows the Moon to cover the Sun nearly precisely in total solar eclipse. This matching of apparent visual size is a coincidence. The Moons linear distance from Earth is currently increasing at a rate of 3.82±0.07 cm per year, but this rate is not constant. - ------------------------------------------------- FORMED 4,5 BILLION YEARS AGO ------------------------------------------------- The Moon is thought to have formed nearly 4.5 billion years ago, not long after Earth. Although there have been several hypotheses for its origin in the past, the current 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. - The Moon is the only celestial body other than Earth on which humans have currently set foot. The Soviet Unions Luna programme was the first to reach the Moon with unmanned spacecraft in 1959; the United States NASA Apollo program achieved the only manned missions to date, - ----------------------------------------- MANS VISITS TO THE MOON ----------------------------------------- - 1 ---- The Soviet Unions Luna programme was the first to reach the Moon with unmanned spacecraft in 1959 - 2 ----- The first manned lunar orbiting mission by Apollo 8 in 1968, and six manned lunar landings between 1969 and 1972, with the first being Apollo 11. These missions returned over 380 kg of lunar rocks, which have been used to develop a geological understanding of the Moons origin, the formation of its internal structure, and its subsequent history. - 3 ---- After the Apollo 17 mission in 1972, the Moon has been visited by only unmanned spacecraft. Of these, orbital missions have dominated: Since 2004, Japan, China, India, the United States, and the European Space Agency have each sent lunar orbiters, which have contributed to confirming the discovery of lunar water ice in permanently shadowed craters at the poles and bound into the lunar regolith. The post-Apollo era has also seen two rover missions: the final Soviet Lunokhod mission in 1973, and Chinas ongoing Change 3 mission, which deployed its Yutu rover on 14 December 2013. Future manned missions to the Moon have been planned, including government as well as privately funded efforts. The Moon remains, under the Outer Space Treaty, free to all nations to explore for peaceful purposes.
Posted on: Mon, 07 Jul 2014 07:14:07 +0000
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