Tomorrow evening, you have the chance to spot a rare natural phenomenon: the blue supermoon. But what exactly is it, and why are we talking about a supermoon and how and where should you look? explains our science expert Martin Peters.
What is a blue moon?
“The moon, like our Earth, is a big rock that doesn’t emit any light,” Martin says. “However, on many nights it stands as a bright spot in our sky. This is because the moon reflects the sun’s rays and its half facing the sun becomes visible to us.”
Exactly where the moon is in relation to us and the sun determines how much light and dark side we can see. “We call this the lunar phases, or phases of the moon,” he continues. The most notable of these is the full moon and new moon, when all sides of the light and dark face us. The 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 “collective month.”
A blue moon is rare, but not exceptional
Martin Peters, science expert
This means that in most cases we have one full moon every month during the year. Usually, but not always. Because such a synodal month does not completely correspond to the months of our calendar. “Every 2.7 years we have an extra full month in a month. The second full moon of that month (visible this year on August 30) is called a Blue Moon. This term probably originates from the English expression “Once in a blue moon’, which means that something rarely happens. So a blue moon is rare, but not exceptional.
But beware, this definition of a blue moon actually came about in 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 refers to the third full moon out of four In one sidereal 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, we see the monthly moon. You won’t get to see the next seasonal blue moon until August 19th. 2024. The next monthly will be on May 31, 2026.”
To be clear: a blue moon doesn’t suddenly turn blue. “Although it’s not impossible,” says Martin. “The composition of the atmosphere can affect the sunlight reflected by the moon 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 Krakatoa Then people actually saw a blue moon in the sky.
What is a supermoon?
However, the blue moon is not only the second full moon in a month, but also the so-called “supermoon”. A term denoting 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 closer to the Earth and sometimes farther away. The shortest distance is the perihelion and averages about 363,300 km. In this case we are talking about the supermoon. The largest distance is the apogee and averages about “405,500 km. Then one talks about a micromoon. While there is a difference in size and brightness between the extremes and a ‘normal’ moon, we wouldn’t notice it when we looked up.”
“The blue supermoon – which can be seen at night from Wednesday to Thursday – can be seen early in the morning around 3.30 am,” Martin adds. “The moon will then be about 357,344 kilometers from Earth. The giant moon is best seen from an area with dark skies and limited light pollution. Using a small telescope or binoculars, you can see the surface of the moon in more detail. If the weather is clear and dry, it can produce Beautiful pictures.”
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