PHILADELPHIA (AP) - A rare "black moon" rises Friday night over the Western Hemisphere, but don't expect to see it.
NASA says a black moon is the second new moon in a calendar month. A new moon is the start of the lunar cycle and the phase where the moon is impossible to see because it's completely shrouded in darkness.
A black moon occurs about once every 32 months. Friday night's officially takes place at 8:11 p.m. on the East Coast.
The term "black moon" contrasts with "blue moon," which is the second full moon in a calendar month.