Naming convention for moons of exoplanets?

I'm planning a science fiction story that takes place partly on the moon of a gas giant orbiting another star. For the sake of a bit of realism, I want to give it a plausible-sounding official name. As far as I'm aware, no one has yet discovered a body in orbit around an exoplanet. Does anybody have any idea what sort of naming convention astronomers would apply to such a body? Or would they not worry about that question until somebody actually found one?

If it makes a difference, the gas giant in question is 55 Cancri f.


Thanks everyone. 55 Cancri will be where humans make first contact with an advanced alien civilisation. They allow the colonists to settle on the moon. What the colonists should call it is a bit of a sore point among them. Some want to use the aliens' name (or as near as humans can pronounce it), some want to pick their own name (say, from Shakespeare or Sumerian mythology), and some want to play it safe by using the astronomers' name - 55 Cancri f plus a Roman number sounds the most likely choice for that.

4 Answers

  • Chris
    Lv 7
    1 decade ago
    Favourite answer

    Generally exoplanets are almost never given official names. They're named after the orbiting star's catalogue name with a letter from b- onwards (a designates the star).. so 55 Cancri f is the 5th planet out from 55 CNC. Educated guess then would make me assume that if technology ever gets to the point we can see an exo-moon, it would be given a roman numeral designation, so if that planet had 3 moons they'd be 55 CNC F i, 55 CNC F ii, 55 CNC F iii, for example. But if we were ever actually going to an exo-world of any sort, I'd assume at that point the colonists would probably have given it some sort of common name.

  • 1 decade ago

    Well, you can see how they name the exoplanets: simply appending a lowercase letter to the star name. So, your gas giant is the 6th planet around 55 Cancri. I would guess that they might use roman numerals as a logical way to denote moons, so if you wanted to talk about the the third moon of your gas giant, you could write 55 Cancri f III.

    But the planets (and moons once they are discovered) probably will not have 'normal' names like we have here in our Solar System because there are simply too many of them. links to a proposal, but I don't think it mentions moons (I didn't read the whole paper).

    Interesting idea, but I think the idea of naming planets is flawed. Although we may not be able to travel to the stars in a practical way right now, and even though we haven't found life elsewhere (yet), I think it is highly arrogant to give a name to something that is not ... ours... . What if one day (in the far future!) we go there and find lifeforms, they will obviously have a name for their planet. That's the name we should use. For the time being a simple designation is useful but anything else...

    Followup note: It is important to keep track of upper and lowercase!! Uppercase letters refer to stars in a multi star system!! 55 Cancri A would refer to the primary star in a multi-star system. 55 Cancri F is the 6th star...

    55 Cancri B f would refer to the 6th planet of the second star, a very exotic system!

  • 1 decade ago

    We can barely discover exoplanets themselves. Most are just discovered by stellar wobble of parent star or of eclipsing the parent star.

    The moons of said planets are far beyond our capabilities to discover.

    When you discover the first exomoon, you can make up the catalog naming convention for them.

    Thanks though for mentioning 55 Cancri-f. I find that goldilocks gas giant very interesting.

    Just so you know, the f in 55 Cancri-f DOES NOT mean that it is the fifth planet from its parent star. The f means that it is the fifth planet discovered by human astronomers to exist in its planetary system.

    Look at the Gliese 581 system and you will see for certain of this, because Gliese 581-e is the nearest planet to the parent star in that planetary system.

  • 1 decade ago

    Depends on the premise of your book.

    If it is the name interstellar-travelling earth-origin humans gave it, then I would stick to the greek/Roman characters that seem to predominate the existing naming conventions.

    But it if is the nake of the moon that was given to it by an indigineous people/species, then there is a rather large chance they don't use greek/roman names. In this case, it could be darned near anything.

    You could always go with Shaesperean characters or something. Or start using the egyptian mythos (or babalonian, sumerian, etc,.).

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