2023-08-29 16:12:19
Thursday, August 31, we should witness a relatively rare phenomenon called a “blue supermoon”. But what is hidden behind this name full of promise? Will our satellite actually display a pretty azure hue? We tell you everything.
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Perhaps you have already heard of it: this Thursday, August 31, not only will the Full Moon be a “super-moon”, but it will also be a so-called “blue” moon! On paper, there is something to dream about but, in reality, not really enough to cut three legs off a duck… Firstly because the term “blue moon” only qualifies the fourth moon of a quarter. The duration of a lunar cycle is actually slightly less than a month, it is about 29.5 days. It therefore occasionally happens that a second Full Moon occurs during the same month. But its color will be nothing special, except that it could display a slightly… orange hue.
The Moon will be blue like an orange!
And for good reason: the trajectory of the Moon around the Earth is elliptical. So there are variations in distance. We speak of apogee when it is at its farthest point from Earth (about 405,000 kilometers), and of perigee when it is at its closest point (360,000 kilometers). On Thursday, the Full Moon will occur at perigee and be low in the sky. However, when light enters the atmosphere, it is made up of different wavelengths, each corresponding to a specific color. Shorter wavelengths, such as blue and violet, are scattered more by air particles than longer wavelengths, such as red and orange.
On August 31, the light reflected by the Moon will therefore have to pass through a greater thickness of atmosphere, which will lead to greater dispersion of shorter wavelengths. This is why red and orange colors will be more visible. As the Moon will be closer to Earth, it will also appear about 14% larger, and 30% brighter! Impressive figures, but a difference barely perceptible to the naked eye… In short, a “blue supermoon” will not be synonymous with an impressive spectacle that evening. On the other hand, beware of the tides which are much higher at the time of perigee!
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