What is the blue moon, a significant astronomical event that will take place this Sunday?

This is a date in the diaries of astronomers. This Sunday, the evening of August 22, a “blue moon”, a relatively rare astronomical event can be observed. Be careful though, those who expect the star to change color will be disappointed … the moon will be white, or better yet yellow.

What is a blue moon?

The term “blue moon” actually refers to the second full moon of a month with two full moons or the third full moon of a season with four full moons. This second structure can only be observed this Sunday, August 22nd.

To fully understand this phenomenon, you need to know that the lunar cycle is 29 days, 12 hours and 44 minutes. Every 29.5 days or so, we can see a full moon or at least once a month. But in the end, there are still 11 days in a calendar year compared to the lunar cycle. As a result, two moons can be seen every two or three years. If you miss a Sunday, you have to wait until August 2023.

Where did the word “blue moon” come from?

But why is blue attached to this event? In this case, no expert has provided a clear and rational explanation. In the pamphlet dated 1528 and contrary to the British clergy, we must believe that “if they say the moon is blue, it is true”, note the editor).

Another orbit in Indonesia in 1883, the eruption of the Krakatoa volcano and the gray cloud that followed it made the moon appear blue for a few minutes. If no explanation is found on the Quebec side, the word “blue moon” is said to have come from the bad tradition of the French word “double moon”, which would become “blue moon”.