Rare ‘black moon’ set to rise this weekend. Here’s what it is

KEY POINTS

A rare black moon event will happen Aug. 23.

The new moon/black moon phase is not visible from Earth.

Slightly offset solar/lunar calendars lead to events like black moons and blue moons.

Once every lunar cycle the moon becomes invisible to Earth-bound viewers as the side we can see falls into a full shadow in a phase known as the new moon.

When the antithesis of the full moon occurs twice in a month, or is the third of four seasonal new moons, it earns the non-astronomical moniker of “black moon,” a rare occurrence that will appear once again on Aug. 23.

But “appear” needs to be taken with a grain of salt because this weekend’s black moon, as with all new moons, will pass unseen.

NASA explains that in this phase, the moon is in the same part of the sky as the sun and ri