What Is a Black Moon?

The astronomical spotlight will shine on the Western Hemisphere as September winds down. But this spotlight defies convention, because it is defined by its very lack of illumination. The event is what some people call a Black Moon — the second New Moon to occur in a calendar month. In this respect it mimics the Blue Moon, which typically refers to a second Full Moon in a month.

But you can see a Full Moon. New Moon arrives when Earth’s lone natural satellite passes most directly between t

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