how and where can you see this natural phenomenon?

“The moon, just like our earth, is a large boulder that itself does not emit any light,” says Martijn. “And yet on many nights it stands like a bright dot in our sky. That’s because the moon reflects the rays of the sun and the half facing the sun becomes visible to us.”

Exactly where the moon is in relation to us and the sun determines how much of the light and dark side we get to see. “We call that the lunar phases or phases of the moon,” he continues. “The most notable of these are the full and new moon, with the entire light and dark sides facing us. A full lunar cycle, from new moon to full moon and back, takes an average of 29.5 days. This period is also known as the ‘synodic month’.”

That means that in most cases we have one full moon per month during the year. Usually, but not always. Because such a synodic month does not exactly correspond to the months of our calendar. “Every 2.7 years we have one full month extra in a month. The second full moon of that month (this year it can be seen on August 30) is then called the ‘blue moon’. This term may have originated from the English expression ‘once in a blue moon‘, which means that something rarely occurs. So a blue moon is rare, but not exceptional.”

“But beware, this definition of a blue moon actually came about through an error. One made by James Hugh Pruett in 1946 in Sky and Telescope magazine. He unconsciously oversimplified the original scientific meaning of the term blue moon. It referred to the third of four full moons in one astronomical season. As a result, we are now saddled with two types of blue moons. So we don’t see the ‘real’ seasonal blue moon in the sky at the end of August, but the monthly one. You won’t be able to spot the next seasonal blue moon until August 19, 2024. The next monthly will be on May 31, 2026.”

To be clear: a blue moon does not suddenly turn blue. “Although that is not impossible,” says Martijn. “The composition of the atmosphere can affect the sunlight that the moon reflects back to our eyes. Dust particles in the air from forest fires or volcanic eruptions can act as a filter. This was the case, for example, in 1883 after the eruption of the volcano Krakatoa. Then people actually saw a blue moon in the sky.”

However, the blue moon is not only the second full moon in a month, but also a so-called ‘super moon’. A term that indicates how close the moon is to the Earth.

“Like the planets in our galaxy, the moon’s orbit is not a circle but an ellipse. Sometimes the moon is therefore closer to the earth and sometimes further away. The shortest distance is the perigee and averages around 363,300 km. In that case we speak of a supermoon. The greatest distance is the apogee and averages around 405,500 km. Then one speaks of a micromoon. While there is a difference in size and brightness between the two extremes and a ‘normal’ full moon, we won’t consciously notice it when we look up.”

“The blue supermoon – visible in the night from Wednesday to Thursday – can be spotted in the early morning around 3.30 am,” Martijn adds. “The moon will then be about 357,344 kilometers from the earth. The super moon is best seen from an area with dark skies and limited light pollution. With a small telescope or binoculars you can see the surface of the moon in more detail. If it is cloudless and dry, it can produce beautiful pictures. Currently, the RMI predicts that the clouds and showers of the evening will decrease during the night.

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