It's here! It's here! The rare astronomical event is making its debut in the wee hours of Friday morning.
>> View photos of Friday's blue moon -- from Earth and from the International Space Station
In the meantime, get ready for tonight's viewing with some need-to-knows on what it means when you say "once in a blue moon." And check out some of the images from this morning, already being shared on social media around the world.
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- A blue moon will occur this Friday, July 31, 2015.
- A "blue moon" is not actually blue.
- There are two definitions of a blue moon. It can either be described as the second full moon in a single month or the third full moon in a season with four full moons. It is possible for one blue moon to fall under both categories.
- Normally, a full moon occurs once a month and three times a season.
- For a full moon to occur more than this is somewhat rare, happening once every 2 and a half years on average, which explains the use of the phrase "once in a blue moon."
- The last blue moon was August 31, 2012, almost 3 full years ago.
- The first full moon this month occurred on July 1.
- There are different theories as to why this type of moon is referred to as "blue." One is one of which being that it came from the old word "belewe" meaning "to betray." People may have believed the moon was "betraying" them by being unexpected and out of schedule.
- Because of its rarity, a number of superstitions surrounding blue moons have developed throughout history.
- Interestingly, the blue moon in 2012 also occurred on a Friday.
>> When you can see Friday's blue moon -- and other trending moon stories
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