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Google News feed shows me the following.

What does the term "Super Worm Equinox Moon" mean and has it ever been used before this 2019 clickbait instance?

Super Worm Equinox Moon

uhoh
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    Not to be confused with Moon Worm. – Mike G Mar 21 '19 at 01:45
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    They forgot to add in "Frosty" or "Fiery", depending on if the average temperature outside will be cool or warm. Should also be a Moon "of Doom" or "of Bountiful Tidings", depending on how the stock market's doing. – Nat Mar 21 '19 at 07:33

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All those adjectives being smooshed together signify an uncommon event. That's why you've never seen them together like that before.

All 3 conditions have to hold true:

  1. It's a supermoon, which means the full moon coincides with the moons perigee or nearest approach. That can make it appear up to 30% brighter than one at apogee (farthest away). These happen about every 13 months and it doesn't have to be exact so usually, we get 2 of them in a row, like we did this year. February had a supermoon and so did March.

  2. It's a worm moon, which means it is occurring in the month of March (see @astrosnapper's answer for a better explanation of that).

  3. It's during an equinox, basically the first day of spring (or autumn).

If any one of those isn't happening then it can't be called a Super Worm Equinox Moon.

Apparently, the term supermoon (all one word, by the way) is a relatively recent thing. I tried to view it on Google N Gram viewer, but...

It is a particularly bright full moon and it does deserve to have its own terminology, IMO.

Update: The rarity of the event is certainly relative. I saw a tweet from National Geographic that we also had a super worm equinox moon 19 years ago.

Community
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Octopus
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    We don't see adjectives together like this very often because they don't serve as effective communication; they're just up at the moment as clickbait. – Nat Mar 21 '19 at 07:25
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    Condition two is rather unremarkable. March is guaranteed to have a full moon, and half of all equinoxes are in March. – JAD Mar 21 '19 at 07:40
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    There are "rare events" in astronomy every other day, simply because there are so many combinations of celestial objects. – Eric Duminil Mar 21 '19 at 08:11
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    +1 While those might also all be valid statements, this answer is valid and straightforward, and addresses the question directly, and it reassures me that super worms are not going to appear during the full Moon at the equinox. Whew! That's a relief. – uhoh Mar 21 '19 at 08:34
  • @EricDuminil supermoon at equinox yes, that it's in march? eh... – Baldrickk Mar 21 '19 at 10:22
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    According to wikipedia, the closest perigee is 356,400 km, and the furthest apogee is 406,700 km, with an average distance of 385,000 km. Brightness is inversely proportional to the square of distance, so closest perigee is $(\frac{406700}{356400})^2=130$% of furthest apogee, and only $(\frac{385000}{356400})^2=117$% of normal. Brightness doesn't really help see it better, but it is about 8% larger than normal, or 14% larger than max (same numbers, but without squaring it). – MichaelS Mar 21 '19 at 11:21
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    It may also be noted that the Moon's apsidal precession (which governs which time of the year full moons can be super) is pretty fast at 8.9 years for a full cycle. So -- contrary to my immediate assumption -- just because the vernal equinox full moon in 2019 is super doesn't mean that all vernal equinox full moons are, or even that the next one will be. – hmakholm left over Monica Mar 21 '19 at 11:39
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    @Nat, sure. Before the internet, newspaper headlines were doing it for decades. The OP already referred to it as click bait. I didn't address that. It's simply a descriptive phrase, and it does accurately describe what was in the sky on the night of March 20, 2019. How big a deal that really is is a different question. – Octopus Mar 21 '19 at 17:37
  • No NGrams to plot because you're only graphing up 'till 2008, BTW. (not that you can plot any further). – Lordology Mar 21 '19 at 19:24
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    @Octopus To be fair, your answer's accurate, and I'd ordinarily have $\texttt{+1}'\text{d}$ it for that. My objection was moreso in the phrasing that this is an "uncommon event". Not because that's wrong in a technical sense, but because it's misleading. I mean, say that we accept the premise that every snowflake is unique; then, each snowflake that falls in a snowstorm is a unique event, as the rarest of them all. But then should the media report stories about "rare" snowflake fallings? By the same token, this event may be "uncommon", but like the snowflakes, it seems misleading. – Nat Mar 21 '19 at 22:19
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    According to google trends, supermoon was first used a noticeable amount in march 2011: https://trends.google.com/trends/explore?date=all&q=supermoon – The Guy with The Hat Mar 22 '19 at 00:59
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All the monthly Full Moons are named e.g. list at timeanddate.com, of which "Harvest Moon" is the one people are probably most familiar with. So the March Full Moon is indeed the "Worm Moon" although rarely referred to as such. The extra hyperbole ("Super", "Blood" etc) seems to be a recent (within the last few years) media phenomenon for unknown reasons...

astrosnapper
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    I think "super" refers to the apparent size of the moon due to it being closer to Earth (since the orbit is not perfect and it is sometimes closer and sometimes farther)? And "blood" refers to the reddish color. – Thunderforge Mar 21 '19 at 04:11
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    I agree, but it's at most a few % bigger if the Full Moon is close to perigee so hardly warrants the "Super". The Moon has also been doing this for millennia before the media decided on this recent "rebranding exercise" and I wish they would stop... – astrosnapper Mar 21 '19 at 05:33
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    This answer does not answer the equinox part at all and incorrectly claims that super is a meaningless hyperbole (it does have a meaning, even if it's not all that significant) – Jasper Mar 21 '19 at 10:20
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    @astro: it's at most a few % bigger According to Octopus's answer it is 30% brighter. – TaW Mar 21 '19 at 12:00
  • @Thunderforge While the moon is closer to the Earth, isn't the apparent size increase more so an illusion than it is closeness...at least at the horizon? – Kenneth K. Mar 21 '19 at 12:49
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    Over use leads to fatigue and to "super" becoming "normal" which leads to even more terms being added into the description to try and make the next Full Moon that's slightly closer brighter "extra, really super"... As this APOD shows the difference in appearance between the 2 extremes is very small and IMHO doesn't justify a "super" adjective for something that's barely noticeable. Too much media hype of something that most people would not notice risks alienating people ("is that it!?") leaving little reserve to push something really new & exciting – astrosnapper Mar 21 '19 at 23:54
  • @astrosnapper Yes, that's basically my answer... – David Richerby Mar 22 '19 at 09:46
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A supermoon is when the full moon occurs at the time when the moon is at its closest point to us in its elliptical orbit. This means that the moon is slightly bigger (honestly, you wouldn't notice it unless you made careful comparisons) and a chunk brighter than normal full moons. Except that supermoons happen three or four times every year, so, actually, a supermoon is itself a pretty normal full moon.

In the last few years, the media seems to have latched onto these as EXCITING! EVENTS!, despite the fact that they account for about a quarter of all new moons. In the last year or so, perhaps they sensing that we have supermoon fatigue ("What, another one? There was a supermoon only a couple of months ago..."), they've started putting long chains of adjectives in front of the word "supermoon" to make it sound EVEN! MORE! EXCITING!!1! These adjectives mostly come from traditional names for each month's full moon, but they sound NEW! and EXCITING!! because we don't use them very often in the modern era.

David Richerby
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