The moon turns new on August 21, 2017 at 18:30 UTC. Some will call it a Black Moon, for a reason entirely unrelated to eclipses. More about that below. A moon at the new phase comes most nearly – for any particular month – to passing between the Earth and sun. This August, 2017 new moon makes that pass directly over the sun’s face, causing the much-anticipated August 21 total solar eclipse . On that day, the day of the coming new moon, the moon will pass between the sun and Earth. The moon’s shadow will fall on Earth. Those in the shadow’s path will witness the solar eclipse, a beautiful sight in the sky, and a dramatic turning of day to dark in the middle of the day.
So … Black Moon. Black Moon eclipse. Why that name? The moon will, of course, in this total solar system and all total solar eclipses appear black in front of the sun’s face during the brief minutes of totality. But that’s not why. In this case, Black Moon stems from folklore, that is, from traditional beliefs, customs, and stories of a community. Prior to the internet, these names were passed by word of mouth. Black Moon is similar to Blue Moon, which, by one definition, can be the third of four full moons in a season. Black Moon is the name used for the third of four new moons in one season, with a season being the period of time between a solstice and an equinox (or vice versa).
Most of the time, there are only three new moons in one season. But if the first new moon comes early enough in the season, it’s possible for a fourth new moon to sneak in before that season comes to an end. That’s exactly what happens during the Northern Hemisphere summer (Southern Hemisphere winter) of 2017:
2017 Jun 21: June solstice
2017 Jun 24: new moon
2017 Jul 23: new moon
2017 Aug 21: new moon
2017 Sep 20: new moon
2017 Sep 22: Sept equinox
Of course, all new moons are, essentially, black from our earthly perspective. New moons come once each month, as the moon orbits Earth. On the day of new moon – unless we’re viewing a total solar eclipse, we don’t see the new moon. That’s because a new moon rises when the sun rises. It sets when the sun sets. It crosses the sky with the sun during the day. Its fully illuminated face, or day side, is turned entirely away from us.
Modern techniques – telescopes, filters, photography – have made it possible to see the moon even at the instant it becomes new.
That’s the case with Thierry Legault’s image, below, which he acquired in 2013. Read more about Thierry’s image here.
It’s only as the moon moves in orbit, as its lighted hemisphere begins to come into view from Earth, that we can see it in our sky. Then we see the moon in the west after sunset as a slim waxing crescent – what some call a young moon.
From the U.S. – with autumn approaching – most of us won’t see the young moon again until August 23. It’ll be in the evening sky on August 22, too, but – with the angle of the ecliptic, or sun’s path, slanting low at this time of year with respect to the evening horizon – it’ll be hard to see.
Still, especially if you’re traveling back from the path of totality on August 22 or 23, watch for the young moon. You might catch it along some country highway, in the west shortly after sunset!
As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.
Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.