A Black Moon is not a formal astronomical term but refers to rare and specific New Moon occurrences. There are three main definitions of a Black Moon:
- The second New Moon occurring within a single calendar month. This version of a Black Moon happens roughly once every 29 months.
- The third New Moon in an astronomical season that has four New Moons instead of the usual three, called a seasonal Black Moon, occurring about once every 33 months.
- A rare event when there is no New Moon (or no Full Moon) during the month of February, which happens roughly once every 19 years.
A Black Moon is essentially a New Moon, which means the Moon is not visible from Earth because its sunlit side faces away, resulting in some of the darkest skies perfect for stargazing. It is the opposite of a Blue Moon, which involves Full Moons rather than New Moons.
