A unique celestial spectacle will grace the night sky on Sunday, May 31, as a blue micromoon reaches its peak brightness. This intriguing cosmic event combines a second full moon within a single month with the occurrence of the moon at its furthest point from Earth in its orbit.
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The term ‘blue moon’ does not refer to a change in colour but is a designation for the second full moon in a calendar month, which happens due to the moon’s 29.5-day lunar cycle not always aligning perfectly with the Gregorian calendar. This anomaly creates opportunities for two full moons to be observed in the same month. The expression “once in a blue moon” captures the rarity of such events, adding to the allure of the upcoming night sky display.
This month’s blue micromoon follows the Flower Moon, which illuminated the skies on May 1. As May draws to a close, the sky watchers have reason to be excited about the approach of this rare phenomenon. The upcoming full moon, although likely to appear in shades of amber and orange near the horizon, will certainly draw admiring gazes as it rises.
The phenomenon also qualifies as a ‘micromoon’ because it occurs at apogee, the point in its orbit when the moon is farthest from Earth. According to experts from Time and Date, when a micromoon appears, it can seem approximately 6 per cent smaller than an average full moon and significantly smaller—over 12 per cent less—compared to a supermoon.
For those eager to catch a glimpse of May’s blue micromoon, the prime viewing time will be during moonrise on the evening of Saturday, May 30, shortly after sunset. Observers should look towards the eastern horizon as dusk settles in, where the moon will gradually rise into view.
Despite the name suggesting otherwise, this celestial body will not appear blue. Instead, atmospheric conditions will likely cause it to emit a golden-orange glow, thanks to a phenomenon known as Rayleigh scattering—similar to the vivid hues observed at sunset. Skywatchers will be fortunate, as no telescope is necessary to enjoy the spectacle. However, binoculars can enhance the experience, providing clearer and more dramatic views of the moon’s surface.
Those interested in planning their observation should consult local timings to determine when moonrise will occur in their area, using resources such as Time and Date. This will ensure that they do not miss the opportunity to witness this extraordinary celestial occurrence.
In terms of future blue moons, after May 31, the next monthly blue moon will not happen until December 31, 2028. However, stargazers can look forward to a seasonal blue moon on May 20, 2027, which is defined by astronomers as the third full moon in a season that has four full moons.
With such an unusual pairing of astronomical events, the blue micromoon of May 31 presents an exceptional opportunity for both amateur and seasoned sky watchers alike. It serves as a reminder of the enchanting wonders of our universe, captured and celebrated in the beauty of a single night sky.