“It’s simply the occurrence of two full moons in one month,” says retired high school science teacher Bob Hartley.  Simple, yet so rare and beautiful.  A “blue moon” appears approximately every two and a half years; and only once in every 20 years it appears on New Year’s Eve.  When you’re out and about welcoming the New Year, be sure to look up at the sky and catch this month’s “extra moon” because it won’t appear again for a while.  Keep in mind that while some blue moons may glimmer a bluish hue due to dense particles, most of them unfortunately do not.  The name refers to the unusual pattern of its occurrence.

[Via HomerTribune; Gizmodo; Wiki]