Once in a blue moon – a phrase in English when something only happens very rarely or under very adverse circumstances. But now it’s here, the blue supermoon and marks the end of a series of astronomical phenomena in Berlin’s night sky. We answer the most important questions about the cosmic spectacle.
What makes the supermoon so super?
The term refers to a full moon phase in which the moon is close to the so-called perigee. This is the point in the moon’s orbit with the smallest distance to Earth. The supermoon is therefore nothing more than a particularly close full moon, which appears larger due to the reduced distance to Earth. This optical magnification is accompanied by a brighter appearance.
Why is the blue moon not blue?
Unlike the blood moon, which bathes our satellite in a glowing red or orange light, the color of the full moon does not (unfortunately) change with the blue supermoon. Instead, it refers to an additional full moon in a quarter – i.e. between the solstice in June and the equinox in September. Only three full moons should actually fit into this span, but due to the lunar cycle of 29.5 days, there are shifts every few years that result in a blue moon. The next one will not occur until May 2026!
The nominal misunderstanding can be explained by the English proverb mentioned at the beginning, which coined the name of the moon. In this case, however, blue does not refer to the color, but to a state of mind, “feeling blue”, i.e. a kind of sadness or persistent melancholy. The Anglo-Saxons saw the second appearance of the moon in just one month as an unusual situation that could only put the moon in a sad mood. Werewolves can probably only agree!
How common is Once In A Blue Moon?
Despite the fact that the saying is synonymous with an extremely rare event, blue moons occur relatively frequently and, above all, predictably. We can look forward to one about every 2.8 years. This is because the moon takes around 29.53 days to orbit the Earth, which is why 13 instead of just 12 full moons occur every 2.8 years. Namely, when the first full moon of a month also falls on the first day of the month and this month does not happen to be February. The next blue supermoon therefore awaits us in May 2026.