There’s an uncommon celestial event happening this weekend, and it only happens once in a black moon. A black moon is the opposite of a blue moon, but it’s just as rare, according to Live Science.
While a blue moon is the second full moon in a calendar month, a black moon is the third new moon in a season of four new moons. The current season began with the summer solstice on June 20 and ends with the equinox on September 22. There were new moons on June 25 and July 24, and there will be more on August 23 (the black moon) and September 21: That makes four new moons in a season, which only happens once every 33 months.
While the black moon can’t be seen with the naked eye, the presence of one does make for optimal stargazing conditions…