Rare blue moon to be seen tonight
The UK will be hoping for clear skies on Friday night to see the blue moon.
Despite the name, a blue moon does not change colour. Rather the name refers to something that happens "once in a blue moon", according to NASA's National Space Science Data Center.
By most definitions, a blue moon happens when a full moon occurs more than once in a calendar month. In this case, we have seen a full moon on 2 July and will see another one again tonight if the sky is clear.
The first recorded English usage of blue moon dates back to 1528, according to the Morris Dictionary of Word and Phrase Origins.
The next blue moon will not be seen until January 2018.
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