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News outlets across the Western Hemisphere are reporting the “rare occurrence” of a “black moon” on the night of September 30.

A black moon, they say, is when there are two new moons in one calendar month. It’s sort of the opposite of a “blue moon,” which signifies two full moons in one calendar month.

But “black moon” isn’t a scientific term, and it isn’t recognized by NASA. Neither is the term “blue moon.”

A black moon is just like any other new moon: invisible to the naked eye. At most, it will provide a dark night sky, ideal for stargazing.

It’s difficult to pinpoint exactly where the term “black moon” comes from. In astrology, there is a connection between the black moon and the character of “Lilith,” mentioned in both Sumerian and Hebrew mythology. The term has also been attributed to the Wiccan religion. Others see all of these “lunar brands” as just another example of “the news media’s obsession with branding.