Blue Moon 2026: a rare solar event is coming this week, here's how to see it in the UK

A blue moon is a full moon that appears twice in the same calendar month, with the upcoming one occurring on 31 May at 9.45am in the UK. This full moon is also a micromoon because the Moon will be farther from Earth, making it appear smaller than usual. Blue moons are rare, typically happening every two to three years, because lunar phases take about 29.5 days and create an occasional 13th full moon within a year. The term originally referred to the third full moon of a four-moon season, and later expanded to include the second full moon in a single month. Moon phases depend on the relative positions of the Moon, Sun, and Earth, since the Moon reflects sunlight.

"On Sunday 31 May, there will be a full moon - the second in the month of May - known as a blue moon. Usually, in each calendar month, there is only one full moon, but May is an exception to this rule. Coincidentally, this will also be a 'micromoon', as the moon will appear smaller than usual thanks to it being further away in its orbit from the earth."

"According to the Royal Observatory, we are due another blue moon on 20 May next year. The last time there was a blue moon was August 2023, according to AccuWeather. It's been a very auspicious time for stargazing and celestial events lately - earlier this month saw the annual Lyrid meteor shower litter the skies."

"'Blue moon' was originally the term for the third full moon of a season containing four moons. Now it's also given to a second full moon in a single calendar month. What makes a blue moon rare is that they only occur every two to three years. Because the phases of the moon take 29.5 days to complete, it takes 354 days to complete the full 12 cycles. But since there are 365 days in a year, this means that approximately every two and a half years a 13th full moon is spotted."

"The phases of the moon are determined by where the moon, sun and earth are positioned. Since the moon doesn't produce light on its own, we can only see parts of it when it is light up by other objects. Distant stars emit a small amount of light and earthshine, the reflection of light from the earth, can all help showcase some of it, but it's the sun that provides the moon's"

Read at CN Traveller