6 curiosities about the rare Friday the 13th harvest moon

CC BY 2.0 Jon Bunting/Flickr

Here's everything to know about this year's unique September full moon.

The moon is a wonder in all of its phases, but we seem to go a bit loony for her when she's full. And this month, the full moon has a lot going on; enough to make all of us lunar fangirls and boys extra excitable. Consider the following:

1. It's the harvest moon

The full moon closest in date to the autumnal equinox is awarded the title of harvest moon. Given the moon's cycles, this means that harvest moons can happen as early as September 8 or as late as October 7. This year's equinox falls on September 23, and thus the month's full moon will wear the crown.

2. It will provide extra light

Because the harvest moon occurs when the orbit is more parallel to the horizon, its relationship to the eastern horizon stays close to the same for several days. This means that while usually the moon rises around 50 minutes later each night, the harvest moon rises just 25 to 30 minutes later across the northern U.S., and only 10 to 20 minutes later for much of Canada and Europe, according to NASA, which notes. While all full moons rise at sunset, the fact that the Harvest Moon has a shorter rising lag on successive days means that we get what appears to be a full moon rising near sunset for more days than usual; this gave farmers a “sunset extension” of sorts, which went to good use during the very busy time of harvest.

3. It's full just for an instant

True of all full moons – although it may appear full for a few days, astronomically speaking, the moon is full at the moment that it’s exactly 180 degrees opposite the sun in ecliptic longitude. For this year's harvest moon, that means it will be full for a fleeting moment at 4:33 Universal Time on September 14.

4. But for many the harvest moon coincides with Friday the 13th

For those of us in the Eastern time zone, the moon turns full at 12:33 a.m. on Saturday, September 14th – thereby depriving us of the spooky magic of such a mash-up. For the rest of the United States time zones, the moon becomes full officially before midnight on Friday the 13th.

(Bonus fact: Paraskevidekatriaphobia means a fear of Friday the 13th!)

5. A Friday the 13th full moon is relatively rare

We have not had a nationwide full moon on Friday the 13th since October 13th, 2000 – and won’t have another until August 13th, 2049.

6. It will also be a micromoon

Sure, supermoons get all the fanfare for their increased appearance in size ... but let's not ignore the adorable micro moon! This month's full moon nearly coincides with apogee – the point in the moon's orbit when it is farthest from Earth. The difference in moon-to-Earth distance between apogee and perigee is 30,000 miles. This difference in distance makes a supermoon look 14 percent bigger and 30 percent brighter than a micromoon. We love underdogs, go little micromoon!