What to know about tonight's "black moon"

December is coming to an end with a "black moon" on Monday night, Dec. 30, but those hoping to see the phenomenon will be out of luck. 

That's because a black moon is the term for the second new moon to fall in a single calendar month, and new moons appear invisible to the naked eye from Earth. While new moons happen throughout the year, two new moons only fall in a single calendar month about once every 29 months, according to the Old Farmer's Almanac.

The moon will gradually become more visible in the coming days, reaching its first-quarter stage by Jan. 6 and becoming a full moon by Jan. 13, according to NASA.