You’ve heard of a blue moon. Now get ready for a black moon—there’s one coming up the night of July 31
A black moon isn’t as apocalyptic as it sounds. It’s simply the term for the second new moon in a month, and it’s just as unusual as the phenomenon we’ve come to call a blue moon (the second full moon in a month). Both occur about every two and a half years, although they’re not always evenly spaced. The last black moon was in September of 2016, and the next one will happen January 31, 2022.
So what will you see? Well, as far as the moon goes, not a whole lot. A new moon is the opposite of a full moon—the whole disk is in darkness and more or less invisible to us—although because of a phenomenon called earthshine, the disk may be faintly illuminated. Earthshine or no, the new moon also always appears close to the sun, so it will be heading for the Western horizon at sunset on the evening of the 31st. It’s cool to say you were out the night of a black moon—but it won’t be a visually striking event.
That’s not all bad news for sky watchers, though. No moonlight means very dark skies, which means that objects that shine less brightly can be seen more easily. Even without visual aid, you can get some of the best views of the summer of Jupiter and Saturn, both rising in the southeast at about the time the sun is going down. (And if you have even a small telescope, you’ll get a spectacular view of Saturn’s rings.) Summer is a good time generally for meteor showers, and two minor ones—the Southern delta Aquariids and alpha Capricornids—are peaking this week, and a major one, the Perseids, is just getting going. The dark skies will make more shooting stars visible than on a moonlit night. July is also a good time to see the Milky Way as it’s fairly high in the sky at night now, and low light helps with visibility there, too.