“Blue Moon” Graces Night Sky On July 31

The full moon spotted in the sky on July 31 is often referred to as a “blue moon” — not because of its colour, but because it is an “extra” summer moon.

In most seasons there are three full moons, but occasionally there are four, and the extra is called a “blue moon,” giving rise to the cliche “once in a blue moon.”

Full moons occur approximately every 29.5 days, when the moon is directly opposite the sun from the perspective of Earth. “Blue moons” are far more infrequent, with the next one scheduled to occur in January 2018.

TimeAndDate.com said, “Blue moons occur because lunar months are not synched up perfectly with our calendar months. It takes the moon 29.5 days to There are two astronomical definitions of a Blue Moon; both are a type of Full Moon. When the Moon very rarely actually looks blue, it’s because of a certain size dust particles in the atmosphere.

“The phrase, once in a Blue Moon, is colloquially used to suggest that something is very rare. But just how rare, depends on your definition.

“In astronomy, Blue Moon is defined as either the third full Moon of an astronomical season with four full Moon or the second full Moon in a calendar month.”

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Category: All, Environment