It’s safe to assume you’ve heard the term once in a blue moon, which refers to the rare occurrence when there is a second full moon in a calendar month. But you might not have heard the term “black moon.”
However, on Saturday, August 23, at precisely 2:06 a.m. ET, a black moon is taking place. Although it sounds like something out of a dystopian novel, it’s not that ominous. Let’s take a deeper look at what this all means.
What is a black moon?
Much like great artists such as Picasso, the moon goes through phases. The moon’s version is cyclical, lasting around 29.5 days. A full moon occurs when Earth is between the sun and the moon, and the side of the moon facing Earth is lit up by the sun. A new moon is the exact opposite of a full moon. It occurs when the orb is between Earth and the sun—however, the side facing Earth is shadowed and dark, making the phenomenon invisible to the stargazer.
Similar to a blue moon, if two new moons occur in the same month, the second is considered a black moon.
But there are actually two types of black moons. The other type is based on seasons. It is the moniker given to a third new moon in a season of four new moons, which is what is happening this weekend.
For those in the Northern Hemisphere, summer began on June 21, and new moons took place on June 25 and July 24, making August 23 the third in the lineup. (The fourth will take place on September 21, which is just a day before the equinox signaling the beginning of fall.)
How often does this type of black moon happen?
Seasonal black moons only happen about once every 33 months, according to the Time and Date website.
What does this black moon have to do with the Milky Way?
To some degree, our home galaxy, the Milky Way, is always visible in the night sky. During the summer months, the center of this massive grouping of stars, planets, and dark matter rises higher, making it more visible to the naked eye.
A black moon sky is the perfect time to attempt to see the Milky Way, because the night is even darker than normal. So, although you cannot see a black moon itself, it might just benefit your Milky Way viewing.