Skywatching enthusiasts could have the opportunity to see a rare phenomenon Friday night, as the Western Hemisphere will see its second new moon of the month for the first time in at least two years, according to Space.com and other media reports published this week.
Commonly known as a “black moon,” this uncommon event occurs when the Earth-facing side of the moon is new (or fully engulfed in shadow) for the second time in a single calendar month, making it essentially the opposite of a “blue moon,” the second full moon of a single month.
In the western part of the world, the black moon of 2016 will take place on Friday, Sept. 30, but those in the Eastern Hemisphere will have to wait another month to experience this phenomenon. On the plus side, as ScienceAlert points out, that means that the spooky-looking dark moon will essentially coincide with Halloween in those regions.
“As with most new moons, the real sight, or lack of, is not the moon. Instead, it is the light-free star gazing that will be available due to the absence of the moon,” the Houston Chronicle noted. Nonetheless, astronomy fans should make sure they take advantage of this rare opportunity.
So what exactly is a black moon?
With so many different lunar events out there (blue moons, harvest moons, supermoons, blood moons, etc.), you might be wondering just what makes a black moon so special. The funny thing is, we really don’t know for sure because, as ScienceAlert explained, the term has only relatively recently come into use and experts are still trying to pin down its exact definition.
The website explains that some believe black moons only occur once every 19 years or so, when the month of February does not contain a full moon. Others use the term to describe a month that skips a new moon (the phase of the lunar cycle during which both the Sun and the Moon possess the same elliptical longitude). The most common definition, however, is that a black moon is the second new moon in a calendar month, which last happened in March 2014.
According to Space.com, Friday’s black moon is set to begin at 8:11 pm Eastern time (5:11 pm Pacific time) for those in the Western Hemisphere, which includes North and South America as well as some parts of Africa and Europe. The moon will not be visible until October 1 for those in the Eastern hemisphere, however, meaning their black moon will be delayed slightly.
Black moons occur approximately once every 32 months, the website added, and according to the Chronicle, the next one will not take place until July 2019 – which means that if you live in the Western Hemisphere and you want to see what all the fuss is about, you’d better make sure that you check out Friday’s black moon. Otherwise, you’ll have to wait a while to get a glimpse of this unusual astronomical phenomenon.
Image credit: NASA