Black Moon on 19 August: Invisible fourth 'New Moon' in Northern Hemisphere appears due to calendar quirk

A second full moon in a single calendar month is a Blue Moon, and the flip side of this phenomenon, a Black Moon.


On the night of 18 August (around 11am IST on 19 August) a New Moon graced the skies in the Northern Hemisphere.

While it looked like any other New Moon, this near-invisible lunar event is unique due to a calendar quirk, and unofficially called the 'Black Moon'. As per a report in Forbes, Wednesday's New Moon is the third New Moon in a season with four such phenomena. It is not an actual astronomical event but rather a traditional name and occurs once every 32 or 33 months.

If the year is divided into four quarters, each quarter bears witness to three New Moons. However, summer 2020 in the Northern Hemisphere and winter 2020 in the Southern Hemisphere see four New Moons. These events fall on 21 June, 20 July, 19 August and 17 September 2020.

The Black Moon will be more or less invisible, even if the moon is high in the sky.

The Black Moon will be more or less invisible, even if the moon is high in the sky. Image Credit: Te Papa

According to The Old Farmer's Almanac, a Black Moon is a term given to the third new moon in a season of four, when there are two new moons in the same month, or even when there are no new moons in a month. According to the website, "this could only happen in February, and thus is kind of rare, meaning once every 5 to 10 years."

As per a report in Space.com, there are two definitions for Black Moon. Since the lunar calendar almost lines up with Earth's calendar, each month sees one full moon and one new moon. A second full moon in a single calendar month is also called a Blue Moon and by definition the flip side of it is a Black Moon.

The report adds that at the 'new moon' phase the moon is always black and occurs when the moon passes through the same part of the sky as the sun and as such the moon's dark side faces the earth.

However, sometimes the new moon passes directly between the Earth and the sun and people from Earth can see the moon's black silhouette crossing in front of the sun, causing a solar eclipse.


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