Tonight’s pink supermoon may surprise you
Explaining the latest lunar event.
This post has been updated, because you still care about the moons.
Blue moons, black moons, pink moons, strawberry moons, micromoons, supermoons. For some reason, your news aggregation algorithm of choice thinks you really really really want to know all about these moons. “Catch This Weekend’s AMAZING SUPERMOON,” one headline (or, perhaps, 500 of them) will announce. “The Supermoon Isn’t Actually A Big Deal And You’re All Ruining Astronomy,” another will grouse.
The latest example is the first supermoon of 2021—the so-called “Pink Moon”—which will rise on April 26. Here’s everything you need to know about this one, the next one, and all the rest.
What is a full moon?
Look, it’s okay if you don’t know. There are probably loads of folks who walk around pretending they totally know why that thing in the sky seems to get bigger and smaller at regular intervals who totally do not.
The moon orbits Earth, and it’s tidally locked—that means it always shows us the same face, instead of twirling around like our planet does. That’s why you can always see the man on the moon (or the moon rabbit, depending on your cultural preferences) even as the satellite spins around us. But while the moon is big and bright in the sky when it’s full, that’s only because it’s reflecting light from the sun. The moon is also always moving, so it’s getting hit with sunlight at different angles. It’s invisible to us during the “new moon,” because the celestial body is parked right between us and the sun; the so-called dark side of the moon is lit up like a Vegas, but the side we can see is in shadow. A full moon happens when Earth is right between the sun and the moon, so sunlight hits the part we can see. All the other phases are just the transition from one of those extremes to the other.
What is a super moon?
The April 26 Pink Moon is also, technically, a supermoon. It’s one of just two or three that will rise in 2021. But that doesn’t necessarily mean we’re going to see a giant lunar display.
The moon isn’t always exactly the same distance from Earth, because its orbit isn’t perfectly circular. We call the closest point perigee, and the most distant point is apogee. The closest perigee of 2021 will occur in December, when Earth will be 221,702 miles from the moon, and the year’s farthest apogee will occur in May, with the bodies sitting 252,595 miles apart. The average distance between the two bodies is about 238,855 miles, so while not insignificant, these shifts are far from earth-shattering. The April 26 pink supermoon will be 222,212 miles away; the supermoon in May will be just under 100 miles closer. Our third and final supermoon of the year will come in June, depending on who you ask and what definition of supermoon they’re using, so I guess you could call this supermoon season.
The reason you care about this middling change in distance is that it turns a moon super. When a full moon happens close to perigee, it’s going to look a smidge bigger than if it happened at apogee. Maybe. If you’re lucky. Honestly, the difference is not that profound, but if you’re in a position to photograph the supermoon next to something that showcases the slight increase in scale, it can look pretty cool.
A moon’s supermoon status is often the subject of fierce debate. This is because, as EarthSky explains, a supermoon may sound more scientific than a Blood Moon or Worm Moon, but it’s still not a term with a scientific definition. In fact, it was coined not by an astronomer, but by an astrologer named Richard Nolle in 1979. Basically, whether or not a particular moon is a supermoon boils down to how different stargazers (amateur and otherwise) calculate just how relatively close a full moon has to be to be considered super.
And just to really remind you that words are meaningless and the moon is always just the moon no matter what we decide to call it, July 2019′s black moon—otherwise known as a new moon, which is not visible from the ground—was also a supermoon. Yes, the moon made its closest approach to Earth on a night we couldn’t see it. Just because you can’t snap a pic for your Instagram doesn’t mean the moon isn’t super. The closest supermoon of 2021 will also be a new moon. On December 4, 2021, our lunar pal will be just 221,708 miles away—truly spitting distance—but we won’t get to see it.
What’s a pink moon?
Here’s the bad news: While April 26’s full moon is oft referred to as a “Pink Moon,” it won’t actually look pink. Atmospheric conditions can conspire to change the hue of the moon as seen from the ground—NASA has a neat picture of a positively purple one, which is just gorgeous—but there’s no reason to think April’s full moon will look anything but the usual grayish color. The Full Pink Moon is so-named, according to the Farmer’s Almanac, because its April rise often coincides with the blossoming of a pink North American wildflower called Phlox subulata.
Sometimes you’ll see a headline that promises a moon with so many qualifiers it makes your head spin. A superblueblood wolf moon, mayhaps? Lots of websites will tell you that “wolf moon” is the traditional name of the first full moon of the year in “Native American” cultures, which is kind of a weird thing to claim given that there are 573 registered Tribal Nations in the US alone today, not to mention historically. The idea that hungry, howling wolves were such a universal constant in January that all of North America, with its disparate cultures, geographies, and languages spontaneously came up with the same nickname is—well, it’s silly. It’s a silly idea.
The Farmer’s Almanac now lists a handful of alternatives for historical April moon names: Breaking Ice Moon (Algonquin), Budding Moon of Plants and Shrubs (Tlingit), Frog Moon (Cree), and Moon When the Ducks Come Back (Lakota), to name just a few.
Many cultures have traditional names for the full moon in a given month or season, so there’s quite a list to draw from if you’re trying to really plump up a story on a slightly-bigger-than-average view of the moon. But these are all based on human calendars and activities and folklore; you will not go outside and see a pink moon in April (or a moon full of beavers in November, for that matter), though I wish it were so. Full moons can turn up with a slight tint, but that has nothing to do with what month it is.
What is a blue moon?
A blue moon is a nickname for when two full moons fall in the same calendar month. Astronomer David Chapman explained for EarthSky that this is merely a quirk of our calendar; once we stopped doing things based on the moon and started trying to follow the sun and the seasons, we stopped having one reliable full moon per month. The moon cycle is 29.53 days long on average, so on most months we still end up with a single new moon and a single full one. But every once in awhile, things sync up so that one month steals a full moon from another.
In March of 2018, we had our second “blue moon” of that year, to much acclaim. And while that’s not necessarily special in an oh-gosh-get-out-and-look-at-it kinda way, it’s certainly special: We hadn’t previously had two in one year since 1999. In 2018 (and in 1999) both January and March stacked full moons on the first and last nights of the month, leaving February in the dark. The next time this will happen is 2037.
Getting two blue moons a year is rare, but we have individual blue moons every few years. Also, fun fact: not actually blue. A moon can indeed take on a moody blue hue, but this only happens when particles of just the right size disperse through the sky—and it has nothing to do with the moon’s status as “blue.” Big clouds of ash from volcanic eruptions or fires can do the trick, but it doesn’t happen often, and the stars would certainly have to align for two such rare instances to occur at once.
Is there another kind of blue moon?
Surprise! There’s another kind of moon that some farmer’s almanacs refer to as blue. Just as there’s typically one full moon a month, there are generally three full moons a season. And just as there are sometimes two full moons in a month due to our calendar almost-but-not-quite following the lunar cycle (ugh) there are sometimes four full moons in a season. April 2019’s full moon landed right as spring began, leaving enough time for another three (the last rose on June 17, less than a week before summer officially kicked off and long after we’d all started acting like spring was dead and buried). Some breathlessly referred to this as a rare occurrence, but it happens every couple of years.
Weirdly, the blue moon moniker is applied not to the fourth full moon in a season (which actually only happens once-in-a-you-know-what) but to the third. Why? Who knows. What’s the fourth full moon in a season called? A full moon. ¯_(ツ)_/¯
Similarly, the term “black moon” most commonly refers to the second new moon in a calendar month, but can also refer to the third new moon in a season with four of them. The phrase has also historically been applied to months without full moons, as well as months without new moons. Each of these circumstances occur about once every 19 years, and only in February.
What is a micro moon?
It’s the opposite of the super one. Size isn’t everything. In a previous version of this article, I wrote that while we had such a moon coming up in September 2019, we probably wouldn’t see tons of news outlets crowing over the Micro Full Corn Moon. I was only half right: There were plenty of headlines crowing, though they decided to dub it the Harvest Micromoon instead.
This year’s most distant full moon will occur on December 9, and will be 252,245 miles away—more than 30,000 miles farther out than the year’s closest supermoon on May 26.
But as is the case with supermoons, you shouldn’t expect to see a noticeable difference in the moon’s size.
What is a black moon?
You may be familiar with the concept of a blue moon (see above), which rather dramatically refers to the second full moon in a month. A black moon is the same thing, but for the second new moon in a month. This happens about once every three years. What’s it look like? Well, it looks like a new moon. That means you can’t really see it. But by all means, get out there and do some stargazing.
In case you haven’t yet really grasped the fact that all of these moons are just the result of our arbitrary and often nonsensical calendar system, consider this: In some time zones, North America’s July 31, 2018 new moon actually rose on August 1. That means it wasn’t a black moon, because it was the first new moon of August instead of the second new moon of July. Those time zones got their own black moon at the end of August, when we Americans looked up to see our first new moon of the month (which was their second). This is all definitely very important and noteworthy.
What is a new moon?
A black moon may be rare, but what’s also rare is a super-duper-look-at-the-moon article about a new moon. Every 29.531 days, the relative positions of the sun, moon, and Earth conspire to leave our satellite—which doesn’t produce its own light, but shines thanks to the reflected light of our host star—in the dark. The sun’s rays are still striking the moon’s surface, but they’re hitting the (obviously inappropriately named) dark side that faces away from us. The moon appears to grow and shrink in the sky throughout the month thanks to shifts in its position relative to Earth and the sun. Fun fact: while basically everyone knows what a crescent moon is and why it’s so-called, you might not know that the bulbous shape of a moon somewhere between a straight split down its face and a full circle is called “gibbous,” from the Latin for hunched or humped.
What is a blood moon?
Objectively the most metal moon (sorry, black moon), these only occur during total lunar eclipses (which can happen a few times a year in any given location). When the moon slips through our shadow, our planet gives it a reddish cast. The moon can also look orange whenever it’s rising or setting, or if it hangs low in the horizon all night—the light bouncing off of it has to travel through thicker atmosphere there, which scatters more blue light away. But you’ll probably only see that deep, sinister red during an eclipse.
A lot of headlines about moons are just silly (you do not need to be particularly excited about a blue moon, it just looks like a regular ol’ moon), but you should definitely roll out of bed to look at a blood moon if one is going to be visible in your region. But anyone who crams both “blood” and “eclipse” into their moniker for a moon is just trying to win the search engine optimization game; a blood moon is just a lunar eclipse that’s going through a goth phase. Ryan F. Mandelbaum at Gizmodo makes the case that we should really just stop throwing the phrase “blood moon” around and call them lunar eclipses, which is tough but fair, because they’re lunar eclipses and not evidence of bloody battles between the sky gods.
What is a Paschal moon?
You may have heard that April 2018′s pink moon was also a Paschal moon. This is true! That just means it was used to determine the date of Easter Sunday. All of this is just calendar nonsense, and we refuse to go into it any further. We are, however, excited about this Pascal Moon.