# Jovian moons -- enough, already **URL:** \ **Category:** Factual Questions\ **Created:** [April 4, 2003, 6:15pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508 "2003-04-04T18:15:12Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![aubries](https://avatars.discourse-cdn.com/v4/letter/a/53a042/32.png) [@aubries](https://boards.straightdope.com/u/aubries)\ **Post date:** [April 4, 2003, 6:15pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/1 "2003-04-04T18:15:12Z")
58, as of this morning. Jiminy Cricket. My question is in the naming. These things are turning up left and right, and naming them all is going to be a bitch. Is it possible that the last ones simply won’t get named at all? If so, out of fairness, is it possible to revoke the names of the retrograde irregulars that have been assigned so far? (I know we said your name was Erinome, but we’ve been thinking …) Does anyone have an emergency backup plan? There are bound to be dozens more of these things, maybe hundreds. Now what? ---
**Author:** ![Amp](https://avatars.discourse-cdn.com/v4/letter/a/6a8cbe/32.png) [@Amp](https://boards.straightdope.com/u/Amp)\ **Post date:** [April 4, 2003, 6:24pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/2 "2003-04-04T18:24:52Z")
I’ve always wondered why the Sci-Fi standard of naming isn’t used more often. Like we can call then Jovian I, Jovian II, Jovian III, Jovian IV, Jovian V,… and so on. ---
**Author:** ![zev\_steinhardt](https://avatars.discourse-cdn.com/v4/letter/z/97f17d/32.png) [@zev\_steinhardt](https://boards.straightdope.com/u/zev_steinhardt)\ **Post date:** [April 4, 2003, 6:30pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/3 "2003-04-04T18:30:02Z")
> [@](#): > > \*Originally posted by Amp \* > \*\*I’ve always wondered why the Sci-Fi standard of naming isn’t used more often. Like we can call then Jovian I, Jovian II, Jovian III, Jovian IV, Jovian V,… and so on. \*\* Because Sol-1 implies that the planet is the closest one to Sol. Sol-2 is the second closest, etc. We would designate Earth as Sol-3, not Sol-1 (the first one “discovered”). However, we don’t discover other planet’s moons in order of their distance from their planet. So, if we used the convention you descirbed, we’d either have to keep re-numbering them, or they’d be numbered out of order. Zev Steinhardt ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [April 4, 2003, 7:13pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/4 "2003-04-04T19:13:30Z")
That’s right…Gliese 876 has got 2 planets that we know of, and Gl876b is bigger and futher out than Gl876c, but neither have names- yet… (the tradition is that they don’t get names until they are resolved optically I believe) Oh don’t worry, the moons of Jupiter will all get names eventually, the people that [colonise](https://www.orionsarm.com/worlds/Jupiter.html) them will see to that. ---
**Author:** ![Podkayne](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Podkayne](https://boards.straightdope.com/u/Podkayne)\ **Post date:** [April 4, 2003, 7:16pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/5 "2003-04-04T19:16:58Z")
Each moon actually does have a numerical designation, awarded by the International Astronomical Union at the same time that the name is officially selected, and for the reasons **Zev** mentioned, they are numbered in order of discovery. The designation consists of the first initial of the planet and a roman numeral. Ganymede, for example, is JI, Europa is JII, etc. You can find all the designations for the moons of each planet from the satellite fact sheets here: [http://nssdc.gsfc.nasa.gov/planetary/planetfact.html](http://nssdc.gsfc.nasa.gov/planetary/planetfact.html) In practice, these are rarely used, except sometimes for plot labels or something like that. Walk up to an astronomer and ask, “So, how’s SXI doing?” and you’re likely to get a blank look, even if that person studies that object! I suspect that the only limitation on naming will come by size. Eventually we will begin discovering objects down to 100’s of meters in size, or 50 meters in size, etc. At what point will we stop calling it a moon, and just declare it a “moonlet” or something, and give it a moonlet number? Or perhaps we won’t even bother to catalog things that small. ---
**Author:** ![NutWrench](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nutwrench/32/20193_2.png) [@NutWrench](https://boards.straightdope.com/u/NutWrench)\ **Post date:** [April 4, 2003, 7:56pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/6 "2003-04-04T19:56:03Z")
I think there should be at least one moon called “Bob” 🙂 ---
**Author:** ![Podkayne](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Podkayne](https://boards.straightdope.com/u/Podkayne)\ **Post date:** [April 4, 2003, 8:14pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/7 "2003-04-04T20:14:14Z")
William Hershel did try to name Uranus “George.” Well, he wanted to call it “Georgium Sidum,” George’s star, after King George III of England. Luckily, he was overruled. 🙂 ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [April 4, 2003, 8:24pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/8 "2003-04-04T20:24:14Z")
> [@](#): > > William Hershel did try to name Uranus “George.” I’ve heard of names for penises, but that’s ridiculous. And I’ll come up with my OWN names for my body parts if I want to, thank you. . . . Well, you didn’t expect NOBODY to touch that line, did you? ---
**Author:** ![dwc1970](https://avatars.discourse-cdn.com/v4/letter/d/a183cd/32.png) [@dwc1970](https://boards.straightdope.com/u/dwc1970)\ **Post date:** [April 4, 2003, 8:50pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/9 "2003-04-04T20:50:33Z")
There’s an interesting article at [space.com](http://www.space.com/scienceastronomy/moon_definition_040103.html) that addresses this issue. ---
**Author:** ![Sock\_Munkey](https://avatars.discourse-cdn.com/v4/letter/s/aeb1de/32.png) [@Sock\_Munkey](https://boards.straightdope.com/u/Sock_Munkey)\ **Post date:** [April 5, 2003, 8:51pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/10 "2003-04-05T20:51:25Z")
IMHO If the obiting body in question is large enough to qualify as a planet instead of an asteroid then it should be called a moon, if it’s only an asteroid it should be called a moonlet or natural satelite. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [April 6, 2003, 1:10am UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/11 "2003-04-06T01:10:13Z")
> [@](#): > > \*Originally posted by Podkayne \* > William Hershel did try to name Uranus “George.” > \*\* I heard that because of all the jokes they were considering changing the name of Uranus… …to Urectum ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [April 6, 2003, 4:06pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/12 "2003-04-06T16:06:11Z")
> [@](#): > > \*Originally posted by Sock Munkey \* > \*\*IMHO If the obiting body in question is large enough to qualify as a planet instead of an asteroid then it should be called a moon, if it’s only an asteroid it should be called a moonlet or natural satelite. \*\* Problem with that suggestion is that there’s no generally accepted defintion of “planet” or “asteroid”. “Planet” means the nine that we call planets, and “asteroid” just means a chunk of rock orbiting in the asteroid belt. (And even that’s dicey, since there are asteroids that have highly eccentric orbits, like Icarus.) See these two threads: [Speaking of planets…Is Pluto still considered the ninth planet?](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=146669) [Planet or Asteroid?](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=125200) And an article by SDMB’s **Bad Astronomer** on the topic: [A Ball of Frozen Gases](http://www.faz.com/IN/INtemplates/eFAZ/archive.asp?doc=%7BAF052F32-DDA7-11D4-B99E-009027BA226C%7D&width=1024&height=740&agt=explorer&ver=4&svr=4) ---
**Author:** ![aubries](https://avatars.discourse-cdn.com/v4/letter/a/53a042/32.png) [@aubries](https://boards.straightdope.com/u/aubries)\ **Post date:** [April 14, 2003, 8:37pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/13 "2003-04-14T20:37:38Z")
Now it’s 60. Who had 60 in the pool? These are all good responses, but none of them really answer my question. Is there going to come a point when the number of “moons” (however that ends up being defined) becomes too daunting to name them all? I get that they all have designations, but are they really all going to get names? I was just wondering if the IAU has made any promises one way or the other. Five years ago, I had them all memorized.:rolleyes: ---
**Author:** ![I\_Brian](https://avatars.discourse-cdn.com/v4/letter/i/c89c15/32.png) [@I\_Brian](https://boards.straightdope.com/u/I_Brian)\ **Post date:** [April 14, 2003, 8:47pm UTC](https://boards.straightdope.com/t/jovian-moons-enough-already/166508/14 "2003-04-14T20:47:59Z")
The Jovian system is particularly moon rich. Saturn’s is as well, though not so much - no doubt Cassini will change that perception of course. I figure the names will come - once people agree on the requisite definitions - ie, moon, asteroid or moonlet, etc