After the splendid Flower Moon of last May 1stour satellite returns to full phase today May 31stgiving us the spectacle of Blue Moona second full moon in the same month. Our satellite, then, that day will be at its apogee (the point of its orbit furthest from the Earth), so it will appear smaller than usual, which is why it is called microMoon. We don’t miss out!
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Why Blue Moon
Today May 31st we will admire the Blue Moon that has been missing since 2024, but – we always say – our satellite will not be blue. The term, which is not an official definition of the International Astronomical Union, refers to its supposed rarity, in particular from the English expression “once in a blue moon” (“once in a blue moon”), which aims to indicate something that does not occur very commonly (although in reality this phenomenon is not that rare, seeing as it occurs every 3-5 years).
Over the years, two definitions of the Blue Moon have become widespread: the “original” is the one attributed to the third full moon in a season that contains fourand this is a definition that also refers to the ancient English term “belewe“, that is to say “betray”: it is a treacherous moon because it leads one to think that the season is over, but this is not the case.
But in subsequent years, by pure mistake, Blue Moon was also called a second full moon in a monthwhich is the one scheduled for May 31st: as he explains Timeanddatethe confusion was notably first made by the amateur astronomer James Hugh Pruett (1886–1955), who reported this definition in an article published in the journal Sky & Telescope in 1946.
Later the error spread, after the second moon in a month was called Blue Moon in the popular radio program called StarDate in 1980, and then after the definition appeared answered in a 1986 version of the board game Trivial Pursuit. Today, however, it is now considered a second definition rather than an error.
What does microMoon mean
As he reports again Timeanddatea micromoon occurs when the full moon or new moon coincides with theapogeethe point in the lunar orbit farthest from Earth. In fact, our satellite orbits our planet in an elliptical orbit, which means that one side of the orbit is closer to Earth than the other.
Although there is no universally accepted definition, there is a tendency to consider micromoon a moon whose center is at more than 405,000 kilometers from the center of the Earthconsidering that the average distance between the Earth and the Moon is 382,500 kilometers.
The angular size of a micromoon is 12.5%-14.1% smaller than that of a Supermoon and 5.9%-6.9% smaller than that of an average full Moon (in the years 1550-2650), therefore a micromoon appears smaller than a Supermoon but also than a “normal” full moon.
What we will admire on May 31, 2026
The moon was technically full today May 31st at 10.45am Italian timebut to see it in its splendor we will naturally have to wait until it is dark (on the map the tonight’s sky May 31, 2026 at approximately 11.00 pm), when we can really admire the spectacle of Blue microMoon.
Don’t miss it!
Sources: Moongiant / Timeanddate/Micromoon / Timeanddate/Blue moon
