- A rare harvest micromoon rises in the night sky this Friday the 13th. The September moon will appear smaller than normal as it reaches its furthest point from Earth.
- People across North America and Europe have used full moons to track the seasons and months for thousands of years.
- Here are some of the names they've used for each month's moon.
- Visit Business Insider's homepage for more stories.
On the night of Friday, September 13, look to the skies for a rare occurrence: a full harvest micromoon.
The micromoon will appear about 14% smaller than a supermoon because it will be at apogee — its furthest point from Earth. The harvest moon is the full moon that falls closest to the autumnal equinox in September (or October — the moon doesn't follow the Gregorian calendar). They don't coincide that often.
What's more, a full moon won't fall on Friday the 13th again until August 2049.
Across North America and Europe, people have used full moons to track months and seasons for thousands of years, naming each one based on the seasonal changes it indicated.
The names assigned to full moons are often attributed to the various Algonquian peoples who share a family of languages, living from what is today New England as far west as Lake Superior. Colonial settlers across North America adopted their own version of the indigenous names, according to The Old Farmer's Almanac.
Different languages and cultures characterized their moons differently, sometimes based on agricultural cycles, sometimes on natural phenomena. Here are some of the many names assigned to full moons throughout the year.
Let's get supermoons and micromoons out of the way. Those are contemporary terms that capture how large and small the moon looks at different points in its elliptical orbit.
Supermoons occur is when the moon is at perigee — its closest point to Earth. They can cause stronger ocean tides and weather events.
Micromoons are the opposite of that. Occurring at apogee — when the moon is furthest from Earth — they can reduce the variation in spring tides by 2 inches. They appear about 14% smaller than supermoons, and sometimes seem dimmer, since the area illuminated by the sun appears 30% smaller, according to TimeandDate.com.
The next full supermoon: February 9, 2019
The next full micromoon: September 13, 2019, then October 1, 2020
Astronomy aside, here are the traditional names for each month's full moon, starting with this month.
September: Harvest Moon, Corn Moon, Barley Moon
Over the millenia, this full moon has signified to farmers that it's time to finish harvesting corn and other crops for the winter. It sometimes occurs in October, but is always the moon closest to the autumnal equinox.
Because the harvest moon rises with the setting sun, it looks larger than usual. These bright moonlit nights give farmers a little extra time to harvest their crops.
The next ones: September 13, 2019; October 1, 2020
October: Hunter's Moon, Blood Moon
The leaves have fallen, the deer are fat, and animals are coming into the harvested fields to eat what's left of the grain. Historically, hunters took advantage of October to store meat for the winter.
The next one: October 13, 2019
November: Beaver Moon, Frosty Moon
Beavers are preparing for winter, and so are trappers. This moon signaled trap-setting time, to catch beavers and secure a supply of warm furs before the swamps froze for the winter.
The next one: November 12, 2019
December: Cold Moon, Long Night's Moon
December has the longest, darkest nights of the year, and the moon sits above the horizon longer than usual. It's also cold.
Some Europeans and their descendants in North America called it the "moon before Yule."
The next one: December 12, 2019
January: Wolf Moon, Old Moon, Ice Moon
In midwinter, the story goes, hungry wolves would gather outside villages in North America and medieval Europe, and howl deep into the night.
This one was sometimes called the "moon after Yule."
The next one: January 10, 2020
February: Snow Moon, Hunger Moon
In North America, February marks the depths of winter ,when snow blankets the ground and food is hard to come by. Because it's a shorter month, some years February doesn't have a full moon at all.
The next one: February 9, 2020
March: Worm Moon, Sap Moon, Crow Moon
The air is getting warmer and earthworms emerge from the ground, inviting the robins to return for the feast. Maple trees are ripe for tapping, and the crows' cawing heralds the end of winter. European settlers with religious calendars called it the Lenten moon.
The next one: March 9, 2020
April: Pink Moon, Sprouting Grass Moon, Egg Moon, Fish Moon
The pink moon is named for the pink phlox flowers burst with fresh blooms in spring. The grass sprouts, birds fill their nests with eggs, and fish swim upstream to spawn.
The next one: April 7, 2020
May: Flower Moon, Planting Moon
The flowers bloom in May, and it's time to sow crops again.
The next one: May 7, 2020
June: Strawberry Moon, Rose Moon, Hot Moon
Strawberries ripen for picking in June. Europeans dubbed this the rose moon, and other cultures called it the hot moon for the summer heat ahead.
The next one: June 5, 2020
July: Buck Moon, Thunder Moon, Hay Moon
Deer grow new, velevty antlers this month, and thunderstorms rage aplenty. For Anglo-Saxons, July was all about hay.
The next one: July 5, 2020
August: Sturgeon Moon, Red Moon
Tribes of the Great Lakes and Lake Champlain knew this was the best time to catch sturgeon, an enormous, hearty fish. Some people think the moon looks reddish this month in the heat.
The next one: August 3, 2020
Blue moons are like special bonuses, occurring every two or three years when a month or season has one extra full moon.
When an astronomical season (the time between solstice and equinox) has four full moons instead of the normal three, the third one is a seasonal blue moon.
When a calendar month has two full moons, the second one is a monthly blue moon. That happens because the lunar month is only 29 days long, while the Gregorian calendar month is usually 30 or 31 days long.
The moon doesn't actually appear blue on these special occasions. The moon appears blue very rarely, regardless of its phase, when dust or smoke particles of a particular size cloud the atmosphere after forest fires, volcanic eruptions, or dust storms.
The next seasonal blue moon: August 22, 2021
The next monthly blue moon: October 31, 2020