Halloween is up for a treat this year: a rare blue moon will rise on its night.
For the first time since World War II, a full moon on Halloween will appear in the night sky. This will be on Oct. 31, beginning at 10:49 p.m.
Despite its name, there will be no changes to the actual color of the moon.
There may be a tinge of blue, under certain atmospheric conditions, such as during volcanic eruptions or after exceptionally large fires that leave particles in the atmosphere.
But if the weather turns out to be favorable in your area, it’s best to turn your gaze toward the night sky, since the next Halloween full moon won’t occur in another 19 years.
According to the Farmer’s Almanac, the next full moon rising on Oct. 31 will be in the years 2039, 2058, and 2077, under a pattern known as the “Metonic Cycle.”
A supermoon happens when the moon comes within at least 361,000 kilometers of the Earth while the term blood moon refers to the reddish hue the full moon emits when seen from afar during an eclipse.
The popular definition of the blue moon came about after a writer for Sky & Telescope magazine in 1946 misinterpreted the Maine Farmer’s Almanac and labeled a blue moon as the second full moon in a month. In fact, the almanac defined a blue moon as the third full moon in a season with four full moons, not the usual three.
Though Sky & Telescope corrected the error decades later, the definition caught on.