The Moon will be new on the 25th, and begin waxing crescent until first quarter on July 3rd, when it will wax gibbous approaching full on July 11th. Those observers that consider the moon "light pollution" look forward to this time of the synodic cycle as the moon travels with the sun, keeping the night sky dark, favoring views of distant, elusive, and faint fuzzies - galaxies, nebulae, and clusters.
Remember, as the moon waxes and wanes, you can look forward to those phases where Moon observations are most fascinating. Features appear - mountains, craters, rilles - as the sunlight casts long, defining shadows. Look along the portion of the Moon separating light from dark, known as the terminator, for the greatest contrasts.
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The Moon, unlike other more esoteric and distant astronomical objects, has no named discoverer. Or, one could say that we've all discovered the most familiar of heavenly bodies. Cultures over the ages have created lore of the Moon; mythology is rich for this closest celestial neighbor, as are explanations for its place in the sky.
There are several scientific theories explaining the origin of the Moon. An early theory proposed that the Moon was formed at the same time as the Earth, making it a sister body. This theory, however, cannot explain why the Moon lacks iron. A second idea was that the Moon was formed somewhere else in the solar system where iron was scarce, but this theory, too was discredited when lunar rocks were analyzed and shown to be very similar to Earth's. A third theory suggested that the Moon was spun-off from the Earth as it was forming. While this would explain the similar compositions, a study of the total angular momentum of the Earth-Moon system indicates that the system could not have formed like that. The theory most widely accepted today was first proposed by Dr. William K. Hartmann and Dr. Donald R. Davis of the Planetary Science Institue in 1975 (Hartmann, W. K. and D. R. Davis 1975 Icarus, 24, 505.) Their theory states that very early in the Earth's formation, a rogue body impacted the infant Earth, blowing out debris. This debris remained in orbit around the Earth and eventually came together to form the Moon.
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| Max
| Mean
| Min
|
| Angular Size |
33.14 ' |
31.09 ' |
29.04 ' |
| Distance from Earth |
|
384,467km |
|
| Mass |
0.07349 x 1024kg (0.0123 x Earth) |
| Size |
1738.1km @ Equator (0.2725 x Earth) |
| Revolution period |
27.322 days |
| Synodic period |
29.53 days |
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