Eyes to the sky: today is the night of the blue moon

Everyone with their eyes fixed on the sky: today is the night of the blue moon.

An unmissable event for lovers of stars and astrology. Don't be fooled by the name: the moon will not change color. It is just a curiosity of the calendar, defined as the third full moon of a season that hosts four. A unusual event but not rare, which repeats itself approximately every two and a half years: the next one will be in 2024.

Bright and spectacular, the blue moon will light up the sky in the company of the two giant planets, Jupiter and Saturn, which are in the period of maximum visibility. The trio can be observed with the naked eye from all over Italy, weather permitting, and can be admired while parading over Rome and its monuments thanks to the live images of the Virtual Telescope.

“On average we have one full moon per month, as our satellite takes 29,5 days, or just under a month, to complete its cycle. For this reason – explains the astrophysicist Gianluca Massi, responsible for the Virtual Telescope – it happens that, from time to time, we have 13 full moons in a year.” And that's how the name "blue moon" came into use in the Anglo-Saxon world to indicate this "extra" moon.

In the 1930s, the Maine Farmers' Almanac used this term specifically to refer to the third full moon of a season that has four full moons. This definition was later misinterpreted in the 1940s by an author of the Sky & Telescope magazine, which has thus ended up spreading the definition of a blue moon as the second full moon in the same month. Today's will be a true Blue Moon, according to the original meaning of the term: it will be the third full moon of this summer 2021, which has already given us two full moons (June 24 and July 24) and still has a fourth in store for September 21.

“The moon of August 22nd – adds Paul Volpini of the Italian Amateur Astronomers Union (UAI) – It will also allow the less experienced to more easily recognize in the sky the two giant planets, Jupiter and Saturn, which in the central hours of the night will culminate in the south: a few days after their opposition, they will appear larger and brighter than usual".