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Pluto’s Newly Discovered Moons Get Official Names

 The artist's concept above shows the Pluto system from the surface of one of it's tiny moons.Credit: NASA, ESA and G. Bacon (STScI)
The artist’s concept above shows the Pluto system from the surface of one of its tiny moons.Credit: NASA, ESA and G. Bacon (STScI)

Back in February we told you about an online naming contest for Pluto’s two newly discovered, smallest moons (P4 and P5). Now, nearly half million votes later, the moons have their official names.

Formally approved by the International Astronomical Union (IAU), the governing body that officially names celestial objects,  P4,  which is 15 miles (20 kilometers) across, has been named Kerberos, after the three-headed dog of ancient Greek legend. P5, at 20 miles (30 kilometers) in diameter, will now be known as Styx, after the mythological river that leads to the realm of the dead.

The new cosmic recruits join the family Pluto’s three other moons–Charon, Nix and Hydra–all named for characters associated with the Underworld of Greek and Roman mythology.

Dwarf planet Pluto has five moons, two of which have now received their official names. Courtesy of NASA, ESA, and M. Showalter (SETI Institute)
Dwarf planet Pluto has five moons, two of which have now received their official names. Courtesy of NASA, ESA, and M. Showalter (SETI Institute)

Both Kerberos and Styx were fist spotted by the Hubble Space Telescope in 2011 and 2012, as part of a survey of the Pluto system in preparation for a NASA probe flying by the dwarf planet in 2015. The spacecraft, called New Horizon, is still 600 million miles (1 billion kilometers) from the icy planet. But when it arrives in the neighborhood New Horizon is expected to get up-close portraits of Pluto’s recently discovered moons.

Vulcan Controversy?

This cosmic contest, which was started as a public educational initiative by the scientists who found these tiny moons, turned out to be quite popular worldwide. By the time the poll closed there were over 450,000 votes with front runners that included, other than the eventual winners, Persephone,Orpheus and the top vote getter – Vulcan.

However to the dismay of legions of Star Trek fans–and to the moons’ discoverer–the name ‘Vulcan’ did not make the grade with professional astronomers . It had been proposed by actor William Shatner, a.k.a Captain James T. Kirk.

“The IAU gave serious consideration to this name, which happens to be shared by the Roman god of volcanoes,”read an official statement from the SETI Institute, which had sponsored the naming contest. “However, because that name has already been used in astronomy, and because the Roman god is not closely associated with Pluto, this proposal was rejected.”

Within minutes of the announcement Shatner tweeted his disappointment.

What would Mr. Spock have to say about this decision?

Follow Andrew Fazekas, the Night Sky Guy, on Twitter and Facebook.




  1. Sam Sharp
    July 21, 2015, 5:11 am

    One hundred years ago when Abdul’Baha the son of Baha’u’llah visited Canada and America in one of his talks he clearly stated that Pluto had five moons.” Science should sustain Religion and Religion Should explain science were his other words.”

  2. Abdullah Omar Nasseef
    December 2, 2013, 11:43 am

    I will vote the name thiviploton

  3. Matthewvelasquez
    Currie Middle school
    September 17, 2013, 8:05 pm

    No pluto can’t be a planet again because people say it was blown into pices

  4. Aleksandra
    Belgrade, Serbia
    August 8, 2013, 3:24 pm

    Ara fish! Ara fish! 🙂

  5. Jeremy Keller
    July 3, 2013, 11:35 am

    Prior to the discovery of Charon it was assumed that PLuto had no moons. Now it seems that Pluto has at least five. That piece of artwork is obviously an artist’s concept. But how would Pluto REALLY appear to an observer standing on the surface of that moon? I would really like to know this.

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  6. Ian Mackay
    Glasgow, Scotland
    July 3, 2013, 10:39 am

    Surely Cerberus is the more common form for the 3 headed underworld dog. The other form Kerberos is already used as a common computer security protocol, so it’d be nice if there was a distinction: Cerberus for the moon, and Kerberos for the protocol.

  7. Hefesto
    Somewhere in time
    July 3, 2013, 9:54 am

    Hey, haters, buy a τηλεσκόπιο and look for your own planets and moons… and then name them!
    And no, I have nothing to do with Hades!!!

    Hades -> Pluto
    Hefesto -> Vulcano
    Greek -> Roman

  8. Danny Ellis (Ash Walker)
    July 3, 2013, 7:52 am

    After reading a this post on FB (where I ‘follow’), I was a tad surprised to read comment after comment about Pluto’s ‘sub planet’ status.

    The argument that Pluto must be a planet if it has a moon is invalid, since “a moon is a body that circles a larger planet or body”.

    To be a planet, a body must meet certain criteria, which Pluto does not.
    “1) is in orbit around the Sun
    2) has sufficient mass to assume hydrostatic equilibrium (a nearly round shape),
    3) has “cleared the neighbourhood” around its orbit.”

    Personally, I find the naming of the new ‘dwarf planet’ subclass a suitable cure to the pains of Pluto’s demotion.

    “Plutoids are celestial bodies in orbit around the Sun at a distance greater than that of Neptune, that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit.”

    Now if you’re still not happy, we have the the verb “to pluto (preterite and past participle: plutoed), which was coined in the aftermath of the 2006 IAU decision.”

    Finally, you could always report this post as spam or ‘unfriend’ me, for accepting change, & for possibly promoting it. I know it’s terribly sad, but Pluto is no longer a planet. If anyone needs a hug, there are apps for that. 😛

  9. Ira
    Denver, Colorado
    July 3, 2013, 3:16 am

    Brian- “its”, without an apostrophe, indicates possession. While “it’s” is a contraction for ‘it is’ or ‘it has’. I suggest you brush up on your Grade 4 English before criticizing others.

  10. Thorsten Heil
    July 3, 2013, 3:07 am

    Hecate – The Goddess of The Underworld

  11. Alexander
    July 2, 2013, 7:06 pm

    I’m still disappointed that Hekate wasn’t even an option, but I’m glad they overturned the Vulcan vote… it wouldn’t have made much sense.

  12. Stan Reeves
    Athens Ohio
    July 2, 2013, 6:29 pm

    is this the same body that demoted Pluto in the first place? how can you not honor the top vote getter? They should take everyone of these “scientists” line them up and shoot every last one of them… they are nothing but trash and rubbish

  13. Ryan
    July 2, 2013, 6:17 pm

    Technically speaking (though there is no technical definition of a moon or natural satellite) a moon is a natural satellite orbiting another celestial body. Therefore Pluto does not have to be a planet to possess moons.

    Also by this definition, though the situation hasn’t come to pass, a moon itself can have a moon. This, however, would likely have a highly unstable orbit.

  14. Evan
    Winchester, VA
    July 2, 2013, 6:12 pm

    If a planet is named, and learned about by the world, then gets taken off the “official” planet list, then is considered a dwarf planet, but yet they find moons belonging to the dwarf planet’s gravity field, and are named, shouldn’t we be considering re-enlisting Pluto as a planet? It has it’s own gravity and moons in orbit. To me, that is a planet. So, regardless of the names of the moons, Pluto should be a planet again. otherwise we are naming asteroids that mean nothing essentially.

  15. Sherida Gunness
    Trinidad and Tobago
    July 2, 2013, 6:03 pm

    The names are logical? Is this a serious consideration? How can a non-planet have moons? NASA needs to revise its definition of a planet it seems. Either that or call Pluto and others an asteroid belt :p

  16. Frank G. Gerigk
    Black Forest, Germany
    July 2, 2013, 5:58 pm

    I am very thankful that my proposal “Kerberos” for P4 was chosen. Before the voting, when I saw the proposal of Mr. Shatner, I was aware that there would be no chance for me to give a more popular name for P5. But his second proposal, “Remus & Romulus” for P4 & P5, could not persuade the voters. Until yesterday, I was sure, that Shatner’s “Vulcan” would be successful.

  17. awaked
    July 2, 2013, 5:53 pm

    Pluto is a dwarf-planet, still a kind of planet-ian object. so: moons are cool 😀

  18. M. Bacon
    July 2, 2013, 4:28 pm

    Artist: G. Bacon , My Dad, & Brother are artist and also, G.K. Bacon. Interesting also, have a cousin from North Dakota B. Bacon an artist mainly Bill Board Sign Art. Art must run in the Bacon’s DNA.

  19. Richard L. Kent Esq.
    July 2, 2013, 4:09 pm

    I was pulling for Mickey and Donald.

  20. Brian
    July 2, 2013, 3:57 pm

    “Its” versus “it’s” in the picture caption, please. I expect better penmanship from National Geographic.

  21. S. Kyle Davis
    United States
    July 2, 2013, 3:45 pm

    Spock would say that it is only logical.

    “[T]hat name has already been used in astronomy, and because the Roman god is not closely associated with Pluto.”

    Both valid points, and ones Spock would understand.

  22. Daniel
    Seattle, WA, USA
    July 2, 2013, 3:20 pm

    Nice try, Captain Hell Toupee.

    I’m a little sad that Persephone/Proserpina didn’t get enough votes, but I suppose that a moon of that name would need a 6 month periodicity… maybe a comet that passes by both Pluto and Ceres?

  23. Theresa
    July 2, 2013, 3:15 pm

    It’s only logical.

  24. Chris Smith
    Lake Atitlan, Guatemala -- inside a Volcano in Central America
    July 2, 2013, 3:11 pm

    Pluto and Vulcan not closely related? Nonsense. Pluto is he God of the Underworld and Vulcan’s forge was under the earth. They were neighbors. Shatner was right. And he tried to lend his “Street Cred” to popularize Astronomy. Tssk!

  25. Steve Thomas
    July 2, 2013, 3:06 pm


  26. Mr Spock
    July 2, 2013, 3:00 pm

    Their conclusion is irrefutably logical.

  27. Ted
    July 2, 2013, 2:59 pm

    Can a non-planet have moons?

  28. Dannyboy
    July 2, 2013, 2:59 pm

    Ok so can Pluto be a planet again now???