This year’s celestial calendar is in full swing, with the next visual treat primed to appear in the night sky on Sunday, March 28: the Worm Moon. This particular moon will be large and easy to spot as it hangs high above the Earth, as it always does during its annual March appearance. Here’s more background on the Worm Moon and how it derives its earthy name.
What’s a ‘Worm Moon’?
The Worm Moon is March’s full moon. Every month has a full moon, with some exceptions, as not all full moons are created equal. If we’re being hyper-specific, a true full moon only exists under certain conditions.
Only when the moon, Earth and the sun are perfectly aligned is the moon 100% full, and that alignment produces a lunar eclipse.
Most laypeople are unbothered by this cosmological minutiae, but the Worm Moon will meet this criteria on Sunday, March 28th at 2:48 p.m. ET. When the sun, moon, and Earth are perfectly aligned, the moment is known as “syzygy,” which is the underlying concept behind a true full moon.
Where did the Worm Moon get its name?
It actually turns out to be a squirmy question. According to the Farmer’s Almanac, the name is attributable to the 18th century explorer Captain Jonathan Carver, who coined the term “Worm Moon” because of the beetle larvae that emerged in the Earth once soil began to thaw in the springtime sun. There’s also the more generalized explanation of the moon garnering its name from worms that became visible in thawing soil around this time of year.
There have been other names given to this moon over the centuries, most of which originate from Native American tribes.
Some of those are listed below, per the Alamanac:
The Sugar Moon (Ojibwe) marks the time of year when the sap of sugar maples starts to flow.
The Wind Strong Moon (Pueblo) refers to the strong windy days that come at this time of year.
The Sore Eyes Moon (Dakota, Lakota, Assiniboine) highlights the blinding rays of sunlight that reflect off the melting snow of late winter.
How to see it
The worm moon is a three-day treat, stretching out between Friday, March 26 (tonight) and its peak on Sunday, March 28. Monday, the 29 will also showcase the moon at 99% of its peak brilliance (meaning you probably won’t notice the difference).
The best time to see the Worm Moon is when the moon rises on Sunday (18:48 Universal Time), so check to see when that happens where you live.
Is it a supermoon?
The definition of a supermoon is an inexact science—and really only a term that’s used somewhat arbitrarily by news outlets for clickable headlines. But the term stems back to astrologer Richard Nolle, who in 1979 coined the term for a “either a new or full moon that occurs when the moon is within 90% of perigee, its closest approach to Earth.”
There’s some uncertainty regarding the Worm Moon’s classification as a supermoon, however, as the science journalist Jamie Carter explains for Forbes:
A supermoon is a full Moon that occurs within 90% of its closest approach to Earth in a given orbit. That definition gives four supermoons in 2021, of which the “Super Worm Moon” is the first in a sequence. However, this weekend’s full Moon is right on the cusp, with other definitions of a supermoon—including from astrologer Richard Nole (the originator of the term “supermoon”)—suggesting that the “Worm Moon” is slightly too far away to be called a supermoon.
If this moon doesn’t quite get as close to Earth as some others, you can still find solace in the next spate of moons, which all get closer to the Earth and will therefore be considered supermoons with little debate.
As NASA explains:
The full Moons in April and May are nearly tied as the closest full Moons of the year. The full Moon on May 26, 2021, will be slightly closer to the Earth than the full Moon on April 26, 2021, but only by a slim 0.04%!
So even if the Worm Moon doesn’t technically qualify as a supermoon, subsequent ones most certainly will.