NavList:

Russ Sampson, you wrote:
"Applied in recent times, and of unknown astronomical significance. The first element, Mia-, is unexplained.  The second element is the Latin adjective placidus, meaning "calm, gentle" (here in the masculine form)."

Good to hear from you, Russ! I ran a stargazing evening in Scotland, Connecticut a while back, and as I was driving there, I had a certain feeling of déjà vu from... wow, it's been six years. 

Funny you should mention Kunitsch's book today [it was today when I started composing this message]. On Facebook Ian Ridpath also suggested the same today. I do have a copy of that book (my second purchased copy since a loan of my first copy has apparently turned into a "gift"). It's loaded with useful scholarship, but it's mostly of the linguistic analysis variety. With modern names that's less useful (example: there's no mystery where the names Acrux, Gacrux, and Becrux come from as coinages, but who committed these crimes against language? that's an open question!). Clearly, "Maia" as originally written is unexplained, and clearly "placidus" is Latin and in its most common meaning is "calm".

In the meantime, I have solved the puzzle. Thomas Kerigan's mistress in Naples was one Susanna DiCalpa. He called her "Su" in his letters from London. It is said that she helped edit his books and star charts and was herself an avid celestial navigator. Now consider this: take the phrase "Su DiCalpa I am", a sort of declaration of her independence and agency, and write it backwards. You get "ma_i_aplaCiDuS" ="Miaplacidus". And there you have it! Puzzle solved.

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Well, it would be solved if I hadn't just made that all up. Given reversey star names, like "Regor" and "Dnoces" and "Sualocin" and "Rotanev", I just had to consider the possibility of a word game. I even tried anagrams. An online anagram solver showed that Miaplacidus is a letter scramble of "suicidal map". Do we need to call emergency services to warn of Thomas Kerigan's threat of self-harm? He published that threat 201 years ago, but perhaps we have an obligation to try! ;)

More fun with words... Maybe "Maia placidus" is evidence of time travel. See, Maia is often said to mean "waters" (that's the W.H. Higgins theory c.1882, which probably holds little of said fluid, but nonetheless). And as noted, "placidus" means calm. Grabbing some synonyms, Maia Placidus can be translated as "Mare Tranquillitatus", so someone from a year after 1969 is clearly trying to inject a clue into the early 19th century for us in the 21st century to let us know that time travel exists. ... what? ... too far??

Frank Reed