It’s one of the rarest of astronomical phenomenon, and it’s going to take place on New Year’s Eve (at least in places not Australia). It’s a blue moon, and while it’s easy to explain, the phrase’s current connotation is not. Long story short, a blue moon is a second full moon in a calendar month. Tonight is December’s second full moon; this is the first blue moon on New Year’s Eve since 1990, making it doubly rare!
How the planetary event of a second full moon in a month picked up the moniker blue moon is unknown. The phrase “once in a blue moon” has been around for nearly 400 years, but has only been used since the 1940’s to describe the second full moon in a month. The use of “blue moon” to describe a rare event can be traced back to the 1883 eruption of the Krakatoa volcano in Indonesia, when a cloud of dust and ash gave the moon a blue tint.
Image: Brisbane Times