Tonight’s full moon marks this year's first Real 'Blue Moon' (a term suggesting the occurrence of something rare). Normally, there are only three full moons per season (the time between a solstice and an equinox), but because of inherent variability and, in no small measure that we’ve had a number of “supermoons” recently, a [Full] 'Blue Moon' occurs. What does this mean and what is a 'Real' Blue Moon?
It means we will be witness to a “Blue Moon”, the second and third full moon in a calendar month for the season (the summer in the Northern Hemisphere) out of four.
A “Blue Moon” is the occurrence of two full moon phases during one calendar month or the third of four in a given season.
Our last Blue Moon occurred on 31 October, 2020 (Halloween). On that night, the Moon was near Mars. That moon, like most Blue Moons, was blue in name only. We referred to it as a Blue Moon since it was the second of two full moons in a calendar month. Tonight's Blue Moon is different, however. It's a seasonal Blue Moon, the third of four full moons for the season (the time between a solstice and an equinox). Tonight's Blue Moon will crest on August 21-22, 2021 and, as serendipity would have it, it will be close on the sky to Jupiter and Saturn.
Featured image credit: Krieng Meemano/Shutterstock
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