Pluto’s moons named

By Phil Plait | June 21, 2006 2:18 pm

Science Now is reporting that Pluto’s two moons discovered recently have been named: Nyx and Hydra. It’ll be formally announced on Friday.

These are good names: Nix is the goddess of the night, and Hydra was the offspring of Styx, daughter of Oceanus, and the titan Pallas (which is also the name of an asteroid). Pluto’s biggest moon, Charon, is the name of the ferryboat driver who took the souls of the dead across the river Styx to the underworld, and of course Pluto is the Roman name of the god of the underworld.

Update (June 27, 2006): I had originally spelled the moon’s named as "Nyx", but it should be Nix. The name Nyx is actually better, but it was already used for an asteroid! So they used a variant of the spelling for Pluto’s moon.

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science

Comments (22)

  1. Michelle Rochon

    Pretty good names, fitting well too.

    Better than “Xena” for sure…

  2. Scott Mooney

    Or “Goofy”.


  3. Wayne

    It has been my understanding that “Xena” et. al are temporary nicknames. I’d like to know what real names they are going to have, though. They’re probably waiting for “planet” to be defined, so we’ll be stuck with the nicknames indefinitely.

  4. Scott Mooney says: “Or “Goofy””.

    I was pulling for “Chip ‘n Dale.”

    – Jack

  5. Alex Blackwell

    My understanding is that although “Nyx” was proposed as the name for S/2005 P2, the name that was actually approved is “Nix.”

  6. Cool! Rather appropriate, I think, though there are a number of other underworld gods they could have chosen that wouldn’t have had name conflicts.

  7. Claudia

    I was taking an astronomy course when the moons were discovered. My professor was beyond excited. I’m sure she’ll be happy to have two new names to test students on in the fall.

  8. Greek

    Pluto was the ancient Greek god of the underworld. The Romans adopted the name centuries later.

  9. Cris

    Been a little nit-picky but wasn’t the river, Charon the ferryboat driver take the souls of the dead across was Acheron not Styx?

  10. Nigel Depledge

    Greek, I was under the impression that Pluto was the Roman name for Hades (who was the Greek god of the Underworld).

    Cris, you may be right. I was under the impression that Styx was a lake not a river.

  11. Michelle Rochon
    This is the link to see Pluto’s article. It’s a roman name for Hades, yes. The planets are all by Roman names.
    And that’s Charon. If you see the Styx River article,
    you’ll see that him crossing the Styx is a misconception. I thought that too!

  12. Come on people, looking up stuff on a website? That’s almost as bad as looking something up in a book. You’re supposed to check your facts with your gut. Books — and even the more serious websites — are all facts, no heart. Look things up in your gut, or equivalently, in episodes of Futurama. In the series finale, the Robot Devil sings of his upcoming wedding:

    “I will marry her now and confine her to Hell
    (how droll! how droll!)
    Where Styx is a river and not just a band
    Though they’ll play our reception if all goes as planned!

    Styx was also the personification of the famous river, a Titaness who allied with Zeus during the Olympian–Titan wars. Her name translates (and this is quite appropriate) as “hated”, “abhorrent” or “gloomy”; stygian is a related word from the same root. According to one version, Styx was the daughter of Nyx.

  13. Oh yeah, and if you scroll way down on that page to which I linked, you can see that both Virgil’s Aeneid and Ovid’s Metamorphoses use Styx as the river across which Charon ferries the souls of the dead. The problem with calling a statement about Greco-Roman mythology “mistaken” is that there are just too many versions of the stories!

  14. Melusine

    Blake Stacey said:
    The problem with calling a statement about Greco-Roman mythology “mistaken” is that there are just too many versions of the stories!

    Blake stole a bit of my thunder to yet another one of my cranky mythology diatribes while I was trying to find links related to my books. I think the above mentioned encyclopedia (and Wikipedia’s article on Charon) does a disservice by not pointing out that tradition has it that Charon ferried the shades of the dead across the river Styx. Virgil, or more properly Vergil if one prefers, elaborated on the Hades (or underworld) more so than the Greeks, and that is his version–it’s not the final word. In a review of two very useful Greek/Roman mythology textbooks, it is pointed out why, and I think that’s what really matters:

    While M.& L.’s introduction to Roman mythology focuses on the who, what and where of Italic gods, H.& P. provide a fine discussion of how and why the Romans adapted Greek myths. According to H.& P., the Romans transformed Greek myth by redefining deities and emphasizing different ones; by historicizing myth; by politicizing myth; by reinterpreting myth in light of Roman ideals. Summaries (why not Livy himself?) of the stories of Romulus and Remus, and the rape of the Sabine women, illustrate the results of these transformations. In H.& P.’s discussion, then, Roman myths emerge not as pale imitations of Greek myths, but instead as an important, dynamic aspect of Roman self-invention. The downside to H.& P.’s valuable discussion is that it loses sight of the Roman blending of indigenous and Greek material that M.& L.’s account captures.
    Bryn Mawr Classical Review 95.10.16

    Sounds a bit like the Bible, eh?

    So, it’s not a misconception of Charon crossing the Styx, it’s a different version. And even Virgil is hazy about it within one page! He mentions Charon and the river Acheron and Styx. (“From here is a path that leads to the waters of Acheron, a river of Tartarus, whose seething flood boils turbid mud…A ferryman guards theses waters, Charon, horrifying in his terrible squalor.” Then later Virgil mentions Styx. Oh well.

    These two books at the top of this Amazon page, though a bit too pricey are a good place to go if anyone wants a good reference; Morford’s and Lenardon’s “Classical Mythology” is standard college textbook fare, and it has plenty of citations.

    Anyway, I liked Phil’s idea to begin with in that “discovered recently” link. Nyx (aka Nox) and Hydra are OK, but I’d have saved Hydra for some other stellar phenomenon. The cool thing is discovering the moons.

  15. Cynthia

    Considering the strong monotheistic climate of the world, it is encouraging that astronomers are still entitled the privilege to grant gravitationally bound objects with names emerging from pagan mythology. Phrased differently, it is refreshing to know that astronomers are not forced to bow-down to the pressures of world monotheism. Overall, I find that personalities from polytheistic backgrounds hold more provocative and colorful lives and have greater diversity/depth of character than personalities from monotheistic backgrounds. 😉

  16. Carl R. Sams

    Was Cerebus taken? *thinks hard*

  17. Carl R. Sams

    Amend that, Cerberus *embarrased smile*

  18. Really, the only reasonable version of the Hades-Charon-Styx mythology is the modern musical version of Aristophanes’ The Frogs. I mean, what could be more fitting than Nathan Lane as Dionysus?

  19. Troy

    From what I’ve read Cerebrus was rejected because Pluto already is associated with (Mickey Mouse’s) dogs(!) Pluto (the dog) came out in 1930 and most likely was named after the planet (element 94 was also named after the planet not in 1930 of course). The reason more likely is they wanted N and H for New Horizons. I checked it out the pool where the hydra lives is close to the entrace to the underworld. They can use Cerebrus later if more moons are found (I’d wager no more moons will be found but we are pretty far away.)
    And as a post script let me assert the following: Styx (the band) has a pretty wimpy sound to be named after the river that flows through Hades.

  20. I still like the idea of Orpheus and Eurydice…

    Ah well. Too late now, I guess.

  21. Good names but for one slight difficulty – there’s already a constellation named Hydra (“the water-snake”) as well as another called Hydrus.

    Hydra is in fact the largest constellation in the sky albeit fairly faint. Hydra borders (anticlockwise order ecliptic to north) Cancer, Sextans, Corvus, Libra, Lupus, Centaurus,Antlia, Pyxis & Monoceros.
    Its brightest star , Alpha Hydrae is Alphard, ‘the solitary one – at the heart of the watersnake’ (magnitude 2.0) is an orange giant 130 ly off. Hydra also contains the star cluster M48, the spiral galaxy M83 & NGC 3242 the “ghost of Jupiter” planetary nebula.

    Hydrus, ‘the lesser water snake’, contains the sunlike star Beta Hydri (mag. 2.8, 21 ly off) and is sandwhiched between the two Magellanic clouds. It starts near Achernar & its brightest star is also a faint one at mag 2.9 – Alpha Hydri, a Sirian type star 36 ly. from us. B Hydri is actually one of the closer relatively bright stars to the South celestial pole. Bordering constellations are Eridanus-Octans along one axis & Tucana,Horologium, Dorado, Reticulum & Mensa along the other sides.

    With Pluto’s inclined orbit & Hydra’s proximity to the zodiacal constellations of Libra, Virgo and Cancer it seems possible we could find Pluto & thus also Hydra – its moon – in Hydra the constellation if not Hydrus!

    Well okay not with the unaided eye … 😉
    But still!

    Alliteration aside, that strikes me as a less than ideal situation. Personally, I liked the idea of one of the moons being called Persephone for the daughter stolen by Hades. (Greek Pluto) Cereberus, Opheus, Eurydice, Lethe (river of forgettfullness)Styx etc .. seemed good too.

    As for ‘Nyx’ tho’ I’ve really nil to say on it.

    Source : ‘Collins Guide to Stars & Planets’, P.154-157, Ridpath & Tirion,1984.

  22. Alex, you are correct. It was spelled both ways in the original press release! But in a later release I just saw, it said that there is an asteroid named Nyx, so they used a variant of Nyx– Nix– which is evidently also the spelling used by another culture. I have corrected my entry. :-)


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