A ‘blue moon’ is not actually blue – you’ll get to see for yourself on Friday.

As we all know a permanent ‘blue moon’ has risen in the sky above Manchester replacing the red fog which hung over the city for years, that’s just a football thing but, this Friday Deesiders will get to see the ‘blue moon’ phenomenon in the skies above Flintshire.

Whilst this is a fairly rare occurrence, the first since 2012 the next will be in 2018, a ‘blue moon’ it isn’t actually blue, it doesn’t change colour, however the well-known phrase ‘once in a blue moon’ was coined because of it.

What’s the fuss?

There are two definitions of  ‘blue moon.’

One states a ‘blue moon’ is the third of four full moons in one season.

There are three full moons during Summer 2015 – July 2, July 31 and August 28 –  this isnt what is happening on Friday, the next full moon that will qualify is on 26 May 2016.

The second definition is what we will see on Friday

During most years, the Earth experiences 12 full moons, one in each month. But some years, such as 2015, have 13 full moons, and one of those “extra” lunar displays gets the label of Blue Moon.

The lunar or synodic month (full moon to full moon) averages 29.530589 days, which is shorter than every calendar month in the year except for February.

Those extra one-half or one-and-one-half days accumulate over the year, causing some years to have 13 full moons rather than 12.

According to modern folk lore whenever there are two full moons in a month the second is blue, the Science@NASA video below takes up the story.