There’s a black moon rising on Friday in the Western Hemisphere, and despite doomsday predictions, it’s a fairly natural – if uncommon – phenomenon.
A “black moon” is the appearance of a second new moon in a single month, called such because it really can’t be seen. During the new moon phase, the moon is invisible to the naked eye because it’s passing through the same elliptical plane as the sun, with its bright side facing away from Earth.
The last black moon happened in March 2014. In recent months, there have been the appearances of the blood moon and the super moon, all natural and perfectly harmless lunar occurrences.
This month’s first new moon happened on September 1, and the second will rise on Friday after 5:oo p.m. ET.
According to Joe Rao at Space.com, black moons happen around every 32 months. After this one, the next black moon in the Western Hemisphere will be in July 2019. One lunar cycle is only 29.53 days, less than a full calendar month, so there’s usually one full moon and one new moon every month. When two full moons occur in a calendar month, it’s called a “blue moon.” The black moon is supposedly the blue moon’s flip side.
Black moons are “somewhat unusual,” states Rao. Blue moons happen every two to three years. Super moons, which are when a full moon happens during the moon’s closest approach to Earth, occur four to six times a year. Super moon eclipses happen every 20 years or so, while lunar tetrads – four lunar eclipses taking place six months apart – are very rare, sometimes happening within centuries.
Last year, there was an extremely unique blood moon tetrad – four lunar eclipses within an 18-month period.
This month’s black moon only happens for the Western Hemisphere, as when it occurs in the Eastern Hemisphere, it will be October 1, meaning it’s the first new moon of the calendar month instead of the second. However, the east will get its black moon on October 30, or more forebodingly for those who believe it, on October 31 – Halloween.
