A rare “black moon” will appear in the sky this week, offering clearer views of stars and celestial objects due to its proximity to a new moon. The term “black moon” is not an official label in astronomy but refers to a second new moon within an astronomical season.
Every 33 months, a black moon occurs when there are only three lunar cycles in a calendar month or four new moons in an astronomical season. This event makes the stars and celestial objects more visible as the reflected light of the moon is not present during a new moon.
The rare occurrence happens due to the difference between the 30-31 day calendar months and the 29.5-day lunar cycle. Astronomical seasons are also irregular, allowing for black moons to appear at unique intervals.
Black moons can be either monthly or seasonal. A monthly black moon occurs when there is a second new moon in a calendar month, while a seasonal black moon appears as the third new moon in an astronomical season with four new moons.
Source: https://eu.usatoday.com/story/graphics/2025/08/20/august-rare-black-moon-closer-look/85699076007