Tonight the “super blue moon”, here’s what you’ll see and at what time

Tonight for astronomy enthusiasts and others is the evening of the so-called “superluna blu”. Unfortunately the name is very misleading, because the color of our satellite in the sky will be completely ordinary. It will be observable – weather conditions permitting – from 20:26 local time. The origin of the term Blue Moon is controversial: probably of Anglo-Saxon origin, with reference to an unusual event. From the astronomical point of view of “Blue Moons” there are two: a monthly one, which indicates the second full Moon in a month; and a seasonal one – tonight’s one – which is the third full Moon in an astronomical season with four full Moons.

In reality, even the term “supermoon” is misleading and of journalistic origin. From a technical point of view, it is the effect of a phase of the moon in which the satellite is close to its perigee and therefore closer than usual to the Earth, appearing larger by about 6% – in the case of tonight – and brighter than average. Tonight’s moon is also defined “sturgeon moon” apparently because of an ancient almanac of American farmers who used Native American names for full moons starting in the 1930s. The Algonquin tribe, for example, called the August full moon the “sturgeon moon” because it was easiest to catch sturgeon at that time of year in the Great Lakes region. Seasonal blue moons are quite rare, and there is a simple explanation for this. In an astronomical year, there are usually 12 full moons, since a lunar cycle lasts about a month: more precisely, 29.5 days. Consequently, 12 lunar cycles take 354 days to complete, about 11-12 days less than a solar year of 365-366 days. This difference between the lunar and solar years causes an “extra” full moon per season to occur every 2.5-3 years.