### What (the heck) is a Super Worm Equinox Moon?

• 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?

Not to be confused with Moon Worm.

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.

• Octopus Correct answer

3 years ago

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.

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.

Condition two is rather unremarkable. March is guaranteed to have a full moon, and half of all equinoxes are in March.

There are "rare events" in astronomy every other day, simply because there are so many combinations of celestial objects.

+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.*

@EricDuminil supermoon at equinox yes, that it's in _march_? eh...

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).

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.

@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.

No NGrams to plot because you're only graphing up 'till 2008, BTW. (not that you can plot any further).

@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.

According to google trends, supermoon was first used a noticeable amount in march 2011: https://trends.google.com/trends/explore?date=all&q=supermoon