This month's new moon on March 17 is the perfect time for stargazing.
You may not be able to see a new moon, but it's always a special time of the month for serious stargazers. With little moonlight in the sky leading up to, and following, a new moon, it's an ideal time for stargazing. In March, the new moon will occur early in the morning of St. Patrick's Day — Saturday, March 17.
What Is a New Moon?
A new moon describes the lunar phase when our satellite is positioned between the Earth and the sun. From Earth, it appears quite close to the sun, and therefore the new moon appears at sunrise, and sinks at sunset. It's also invisible, because the sun is illuminating the far side of the moon (the side that always faces away from Earth). But that doesn't mean there's nothing to see.
What Can You See During a New Moon?
Although you will see nothing on the day of the new moon — or for about 24 hours afterward — sky-watchers can search for a sliver of a crescent moon the two evenings following. For the best view, head somewhere with a very low western horizon and search the sky just after sunset, when the sun is catching the right-hand side of a young moon.
Because you'll need some height (and few obstructions) your best bet is a west-facing attic window or a nearby hill. And if you're in a city, then an observation platform will do the trick.
For some religions, the new moon is a very significant moment. The Islamic calendar, for example, is lunar-based, and traditionally the Islamic month begins only when the crescent moon is first sighted.
Although its surface is never visible at the moment of new moon, occasionally this phase appears as a silhouette of the satellite as it crosses part (or all) of the sun during a solar eclipse.
Travelers who saw the partial solar eclipse on February 15, 2018 in South America, experienced this phenomenon. And before that, it occurred during the total solar eclipse on August 21, 2017 in the United States.
The next total solar eclipse will be seen over the South Pacific and in parts of South America on July 2, 2019. Solar eclipses can only occur during a new moon, but because the moon orbits Earth around five degrees off the ecliptic (the path of the sun through the sky), they are very rare.
How Do I See Earthshine?
For a couple of nights after the new moon, it's also possible to see Earthshine on the surface of the moon. If you look at the dark area of a crescent moon, you will see some detail, despite the lack of illumination from the sun.
What you're seeing is sunlight reflected off the Earth and onto the moon. There is always Earthshine on the moon, but it's only possible for your eyes to see it when the crescent moon is very slim. By the third night after a new moon, the glare of the moon will overwhelm this subtle feature.
When Is the Next New Moon?
After the new moon on Saturday, March 17, 2018, the next new moon will be on Sunday, April 15, 2018.
What Causes the Phases of the Moon?
The moon is always half-lit by the sun. But as seen from the surface of the Earth, it doesn't always look that way. As the moon orbits the Earth over the course of a month, the visible sunlit portion of its surface appears to wax and wane in size.
It starts its cycle as a new moon, when it's between the Earth and the sun — and only its far-side receives sunshine. From Earth, there isn't much to see.
As the moon slowly moves east, its western side begins to become illuminated: that's a crescent moon. With each passing day, it appears to grow brighter and larger as it drifts farther from the sun. Two weeks after a new moon, our satellite is on the other side of Earth in relation to the sun. Since its near-side is by then fully illuminated from our perspective on Earth, we see a full moon. It then slowly wanes back to a crescent moon over the next two weeks as it completes its 29-day orbit.
How Many New Moons Will Occur This Year?
There are almost always 12 new moons in a calendar year — one for every month. And this is true for 2018. But because the time between two new moons is usually a little less than a month, every few years there are two new moons in one calendar month.