The Moon

118. The Moon

Position not available. Multiple objects or no NGC/IC designation

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

The Moon is thought to have formed about 4.51 billion years ago, not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a hypothetical Mars-sized body called Theia. New research of Moon rocks, although not rejecting the Theia hypothesis, suggests that the Moon may be older than previously thought.The Moon is in synchronous rotation with Earth, and thus always shows the same side to Earth, the near side. Because of libration, slightly more than half (about 59%) of the total lunar surface can be viewed from Earth. The near side is marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters. After the Sun, the Moon is the second-brightest celestial object regularly visible in Earth's sky. 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 gravitational influence produces the ocean tides, body tides, and the slight lengthening of the day.

The Moon's average orbital distance is 384,402 km (238,856 mi), or 1.28 light-seconds. This is about thirty times the diameter of Earth. The Moon's apparent size in the sky is almost the same as that of the Sun, since the star is about 400 times the lunar distance and diameter. Therefore, the Moon covers the Sun nearly precisely during a total solar eclipse. This matching of apparent visual size will not continue in the far future because the Moon's distance from Earth is gradually increasing.

The Moon was first reached by a human-made object in September 1959, when the Soviet Union's Luna 2, an unmanned spacecraft, was intentionally crashed onto the lunar surface. This accomplishment was followed by the first successful soft landing on the Moon by Luna 9 in 1966. The United States' NASA Apollo program achieved the only manned lunar missions to date, beginning with the first manned orbital mission by Apollo 8 in 1968, and six manned landings between 1969 and 1972, with the first being Apollo 11 in July 1969. These missions returned lunar rocks which have been used to develop a geological understanding of the Moon's origin, internal structure, and the Moon's later history. Since the 1972 Apollo 17 mission, the Moon has been visited only by unmanned spacecraft.

Both the Moon's natural prominence in the earthly sky and its regular cycle of phases as seen from Earth have provided cultural references and influences for human societies and cultures since time immemorial. Such cultural influences can be found in language, lunar calendar systems, art, and mythology.
Supplementary Data or Comments

The shots that built this image were taken during daylight (just after sunset), a time when you can get the best detail from the bright areas of the moon as they're not blown out by the contrast between dark sky and light subject. The three 1/1000 images were focused 'by eye' through the viewfinder of the Nikon and then composed and shot manually. Photoshop's Photomerge put the three together and then the background was normalized and the image darkened to make it appear to be a nighttime shot.

Main Image Information

Location Fingal ON
Date Aug 12 2016
Optics Celestron C14 Edge
Filters None
Mount Byers Series II
Camera Nikon D810A
ISO 1600
Subexposures 3
Exposure Length .001
Guider Unguided


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All images copyright © 2006-2020, Rick Saunders
Main text descriptions sourced from Wikipaedia.
Sky position information is based on IP geolocation and is therefore approximate.