The Moon completes about 12.37 orbits of Earth each year. Most years see 12 new moons, but occasionally there are 13. When a season, defined as the period between a solstice and an equinox, contains four new moons, the fourth is called a black moon. The term, first used in astrological circles centuries ago to describe a mythical hidden moon, is now used by astronomers for this rare timing. Unlike the better-known blue moon, which occurs during the full moon phase, a black moon happens during the new moon phase, when the Moon is positioned between Earth and the Sun and its illuminated side faces away from us.
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