The moon is going to disappear… again. (Photo: trasroid/CC BY 2.0)

Can you spot the black moon? This Friday, in the Western Hemisphere, a rare “black moon” will rise in the night sky, according to Science Alert. But don’t feel too bad if you miss it.

The exact definition of a black moon is something that astronomers are still debating. Some define the term as the new moon that skips February every 19 years, while others use it to refer to any new moon that skips a month. But the most widely accepted definition of the phenomenon, and what is going to occur this Friday, is almost the exact opposite, referring to the second new moon in the same month.

The opposite of a full moon, the new moon is the phase when it virtually disappears from the night sky. Now, it’s happening again, making a second moonless night in the same month, and for a rather dark September.

Those in the Eastern Hemisphere will have to wait until October to get theirs. It’s currently scheduled for Halloween.