BLACK MOON

The lunar calendar almost lines up with Earth's calendar year, so there is typically one full moon and one new moon each month. A second full moon in a single calendar month is sometimes called a "Blue Moon." A Black Moon is supposedly the flip side of a Blue Moon: the second new moon in a single calendar month.

A “black moon,” popularly defined as the second new moon in a month. However, this event may not exactly make for good sky-watching.

While a full moon refers to the moment when the moon's Earth-facing side is fully illuminated by sunlight, a new moon refers to the moment when the moon's Earth-facing side is fully in shadow. (Unfortunately, that means the Black Moon will be more or less invisible, even if the moon is high in the sky).

The Black Moon is a somewhat unusual celestial event — they occur about once every 32 months, and they sometimes only occur in certain time zones.

New moons can be readily seen only when they pass directly in front of the sun, causing solar eclipses. Otherwise, sky-watchers must look to the days before or after a new moon, when just a sliver of the moon’s sunlit side is visible from Earth.

A black moon is like the evil twin of a blue moon, conventionally understood as the second full moon in a month.

If anything, a black moon can be a harbinger of new beginnings and festivities: A black moon that fell on September 30, 2016, was followed by a barely visible waxing crescent moon shining down on Rosh Hashanah, the Jewish New Year, and by a growing crescent that marked the beginning of Muharram, the first month in the Islamic lunar calendar.

And due to time zones, a new moon may not always be a true black moon for the majority of humans.