Trick-or-treating may be off-limits in some places this year, but the coronavirus will not stop this special treat in the sky: Two full moons coming in October 2020 — including a rare “blue moon” on Halloween.
The first full moon, nicknamed the “harvest moon,” will be shining on Thursday, Oct. 1, and the other — known as a “blue moon” because it’s the second full moon during the same calendar month — will be glowing in the sky on Saturday, Oct. 31.
Not only will this be a perfect eerie backdrop for Halloween, but a rare one.
The last time a full moon lit up the sky on Halloween night was back in 2001, but only in the Central and Pacific time zones, according to the Farmers’ Almanac. All the U.S. time zones were last treated to a full moon on Halloween in 1944.
How rare is a blue moon on Halloween?
Well, a blue moon on Halloween is as rare as any full moon on Halloween. NASA space expert Tony Rice says a Halloween full moon has to be a blue moon, because moon cycles are about 29.5 days and Halloween always falls on Oct. 31.
So, if there’s a full moon on Oct. 31, it has to be the second full moon of the month — making it a blue moon.
Back to the question of how rare, astronomy experts tell the Farmers’ Almanac a Halloween full moon occurs approximately once every 19 years. But not all the time. During some of those stretches, the moon’s cycle of phases brings a full moon early on Nov. 1 instead of on Oct. 31.
So sometimes, a Halloween full moon is seen only once every 38 years. As mentioned above, the last Halloween full moon in all U.S. time zones was way back in 1944 — 76 years ago. But it happened in some time zones 19 years ago.
When is the next Halloween blue moon?
After Oct. 31, 2020, the next Halloween full moon (also a blue moon) will occur in 2039, 2058, 2077 and 2096, according to the Farmers’ Almanac.
That means the Halloween full moon will be on the 19-year cycle five straight times.
“The good news is that even if the moon is a day or two away from 100% full on any particular Halloween, it can still serve the purpose for a spooky backdrop since most people can’t tell the difference between a 98% illuminated moon and a 100% full moon,” the Farmers’ Almanac notes.
Two cases worth noting: The moon will be completely full on Nov. 2, 2029 and Oct. 30, 2031, so Halloween on both of those years will feature a near-full moon.
What is a harvest moon?
The Old Farmer’s Almanac says the nickname “harvest moon” refers to the harvesting of crops in early autumn in North America, particularly corn and barley, noting: “Around the harvest moon, the moonrise happens soon after sunset for several evenings in a row, which traditionally allowed farmers to have much more light to finish their harvest.”
According to EarthSky.com, the “harvest moon” nickname got popular in the early 1900s because of music. A song called “Shine On, Harvest Moon” was penned in 1908 by vaudeville stars Nora Bayes and Jack Norworth. It later was recorded by many different singers, including Ruth Etting in 1931, Kate Smith in 1933, The Four Acres in 1955, and Bing Crosby and Rosemary Clooney in 1960, according to BING magazine.
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Len Melisurgo may be reached at LMelisurgo@njadvancemedia.com.