A rare lunar phenomenon will happen Friday: a black moon.
It's not nearly as ominous as it sounds.
According to Space.com, a black moon really is just a new moon with a twist: it's the second new moon in a month.
A new moon happens when the moon is between the earth and sun so that the moon's shadow is facing the earth.
So a black moon is pretty much the opposite of a blue moon – which is the second full moon in a month.
Since it'll just be a shadowed moon in up in the sky, there's a pretty good chance you won't even notice it.
In fact, the Washington Post says it will be pretty much invisible to the naked eye.
If you notice anything at all, it'll probably just be that the night sky seems particularly dark since there's no moonlight.
How rare is a black moon?
Well, a new moon usually happens about once a month, because Space.com says the lunar cycle repeats its phases every 29.5 days.
So every 32 months, there will be two new moons – one at the beginning of the month and one at the end.
Other than the fact that it's the second new moon in one month, there's nothing terribly exciting about the black moon.
If you had your hopes up for some night sky gazing, there is something arguably cooler set to happen Friday night.
The Northern Lights are expected to be especially bright again. A bunch of people in Minnesota and Wisconsin reported seeing them Thursday, too . You'll just have to get away from city lights.