Twelve Planets!

[Update1…. Oh no it’s not official! See here.] [Update2: The vote is in… see here.] [Update3: (7th June 2010) Moved the updates 1 and 2 one sentence earlier since, bizarrely, some readers (ahem! you know who you are…) don’t seem to read further than one sentence, or check the posting date, before entering their findings into their homework.] It’s official!* There are twelve planets in our Solar System (so update all the posters, such as the ESA one on the right).

ESA diagram of solar system (outdated)Count ’em:

  1. Mercury
  2. Venus
  3. Earth
  4. Mars
  5. Ceres
  6. Jupiter
  7. Saturn
  8. Uranus
  9. Neptune
  10. Pluto
  11. Charon
  12. 2003 UB313

In addition, you’ll have to add a new word or two to your vocabulary, such as “pluton”, of which Pluto is the prototype. From the 16th August press release of the International Astronomical Union:

16-August-2006, Prague. The world’s astronomers, under the auspices of the International Astronomical Union (IAU), have concluded two years of work defining the difference between “planets” and the smaller “solar system bodies” such as comets and asteroids. If the definition is approved by the astronomers gathered 14-25 August 2006 at the IAU General Assembly in Prague, our Solar System will include 12 planets, with more to come: eight classical planets that dominate the system, three planets in a new and growing category of “plutons” – Pluto-like objects – and Ceres. Pluto remains a planet and is the prototype for the new category of “plutons.”

-cvj

(Thanks Amara!)

(*almost official. It has to be approved, it says.)

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46 Responses to Twelve Planets!

  1. Robert says:

    I am looking forward to the updates for all the astrological software that drifts around on the net. Now, they will have to include Ceres, Charon and the other one in their horoscopes! At the same time, there might be room for upgrades because the sun is not exactly in the classical signs anymore at the times it used to be…

  2. Clifford says:

    Yes, I can see it now:

    “2003 UB313 is rising in Aquarius, so be sure to pursue any relationships with Asimov robots that may arise…”

    -cvj

  3. spyder says:

    I was hoping Amara would report out.
    Of course now we have to change all those mnemonics; so have at it:
    Men Very Easily Make Jugs Serve Useful Nocturnal Purposes
    My Very Educated Mother Just Served Us Nine Pizzas
    My Very Educated Mother Just Served Us Nine Pizzas
    Mother Very Earnestly Made Jam Sandwiches Using No Peanuts
    My Very Easy Method-Just Set Up Nine Planets
    Mary’s Violet Eyes Make John Stay Up Nights Praying
    Mary’s Violet Eyes Make John Stay Up Nights, Period.
    My Very Energetic Mother Just Sat Upon (the) North Pole
    My Very Elegant Mother Just Sat Upon Nine Porcupines
    My very educated mother just sent us nine pickles.
    My very educated mother just served us nine peas.
    My very excellent memory just served up nine planets.
    Man very early made jars stand up nearly perpendicular.
    My Very Efficient Mother Just Served Us Pistachio Nuts

  4. Yvette says:

    “My Very Educated Mother Can’t Justify Someone Using New Planetary Conventions… oh no, they haven’t named the last one yet!!!” What a bunch of silly arbitrary rules.
    Though looking at the above post, perhaps our rule should be that it’s only allowed to be a planet if it fits the mnemonic… “My Very Educated Mother, Christine, Just Showed Us New Planets Charon (and) Xena.” You could just keep adding to the list!

  5. Amara says:

    From Damien Broderick, a writer friend:

    “My very eccentric mother’s cook just served us nine pastry coated xylophones”

  6. Clifford says:

    The “X” being for “Xena”? Are they going to use that name officially?

    -cvj

  7. Amara says:

    Clifford.. no idea! You can follow the Xena naming story here.

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  9. Paul Clapham says:

    Actually, “pluton” was already in my vocabulary. Don’t the geologists have anything to say about one of their technical terms being ripped off?

  10. Clifford says:

    So Paul, what’s a geology Pluton?

    -cvj

  11. Count Iblis says:

    If Charon (Pluto’s Moon) is a planet then why not our Moon? Our Moon is larger than Pluto…

  12. Clifford says:

    Paul, as a high energy physicist, when I heard the term, my first non-serious thought (yes, I have those, you might have noticed) was that it was a basic “quantum of Pluto”. Pluto itself might then be some huge condensate made of lots of Plutons.

    Perhaps a Pluton might be a new massive particle we will one day discover, perhaps at the LHC!

    Ok… back to painting and sketching physics ideas…..

    -cvj

  13. astromcnaught says:

    Count Iblis – Apparently if a planet has a planet-sized object in orbit where the barycenter (center of mass) is within the primary object then the secondary is not a planet. Thus the Moon is not a planet but Charon is.
    Don’t know what we’d do with an highly elliptical orbit though – it’s a planet, no it’s not, yes it is !! (I think)

    An interesting view on the classification of things-orbiting-stars can be found here.

  14. Count Iblis says:

    astromcnaught, thanks!

  15. astromcnaught says:

    My View Embraces Moving Classifications, Just Stop Uncovering New Planets Called 2003 UB313

    Took 2 cups of coffee that one and I gave up trying to think of a word that started with ‘2’ 🙂

  16. Paul Clapham says:

    My son’s the geologist, but as far as I recall a pluton is a big lump of igneous rock — let me just check Wikipedia — it says “Bodies of magma that solidify underground before they reach the surface of the earth are called plutons”.

  17. I think it’s silly.

    Pluto, Charon and that other thing is just Kuiper belt junk that ended up to close to the sun. I don’t feel they should be included as planets. Same goes for Ceres.

    The moon raises an interesting point. It’s about 1/3 the size of the earth if I can remember correctly, so why not include it.

    Also, I feel that the naming should be consistent, so that earth should be systematically called Terra and the moon Luna. But that’s just me I guess.

  18. “Apparently if a planet has a planet-sized object in orbit where the barycenter (center of mass) is within the primary object then the secondary is not a planet.”

    D’oh! Just read that. Makes sense.

  19. Elliot says:

    I don’t know whether to take all this Ceresly or not.

  20. In The Times on August 16, Alan Hamilton suggested two mnemonics with musical themes:

    My Very Eccentric Mother Called Janet Sang Utter Nonsense Playing Charlie’s Xylophone

    and

    Most Victorian Euphoniums Make Cats Jump Suddenly Unless Neighbours Play Calming Xylophones

  21. Clifford says:

    Most Victorian Euphoniums Make Cats Jump Suddenly Unless Neighbours Play Calming Xylophones

    Wow! that one is brilliant!

    -cvj

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  23. Brian says:

    Our class is learning about the solar system but …………………….we done a assingment to make a model of the solar system BUT why is pluto’s moon a planet (strange?). the reason why why didn’t anyone know about Xena and Ceres???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????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ye i like your website……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….Bye

  24. Clifford says:

    Yvette: – your Mnemonic has a fan or two over at Nature blogs…..

    -cvj

  25. Clifford says:

    Brian, hi. THe point is that the Pluto-Charon system is not like the Earth-Moon system… more like a loosly connected binary planet system. Their barycenter (common point about which they orbit) is not inside either body, unlike in our case where the barycenter lies well inside the earth.

    -cvj

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  28. Brad says:

    Within a week, we have lost 4 planets. We now have 8, Pluto and the 3 new planets are no longer “planets”.

    http://www.cnn.com/2006/TECH/space/08/24/pluto.ap/index.html

  29. Clifford says:

    Hi Brad,

    Yes, I announced this on another post on the blog two hours ago.

    Cheers,

    -cvj

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  31. lydia says:

    Oh no! Pluto, Charon, and 2003 UB313 aren’t planets anymore! Now what do we do for acronyms???????? 🙁

  32. kk says:

    planet is πλανητης in greek means traveler. define first what is a planet and then see u r wrong

  33. YOKOLAND says:

    SWEET!!!

  34. stefan says:

    Since someone has brought back this thread, let me just mention that 2003 UB313 has, in the meantime, officially being named Eris, and its moon is Dysnomia.

    Well, and officially, it’s not a planet anymore, but another dwarf planet – and it’s more massive than Pluto!

    Cheers, Stefan

  35. Clifford says:

    Hi Stefan,

    Yes this post is very old and there have been several more posts on the planetary matters since then (look in the pingbacks at the end of the comments, for example). Thanks for the additional info.

    -cvj

  36. Amara says:

    If you want to think about a an ODD dwarf planet, choose Sedna. It is not a Kuiper belt object, instead it is an _inner Oort Cloud_ body with a _circular_ orbit (!). and why doesn’t it have a moon? See Mike Brown’s Sedna page for why these are strange factinos and more.

  37. addycat says:

    I’m glad that all of these comments are here – I learned a lot without having to click around. 🙂

  38. Minka says:

    Well this is a gowno website i can’t even see what planets are what! and i’m doing a solar system project and it’s due this Wenesday!

  39. kandii says:

    omg! u have got 2 be kiddin’! 12 planets! omg! my teach is going to b hecka suprised!

  40. kandii says:

    ohhhh! i forgot! lolz hey everybody, i am doing this report (sorta) where we have to um, make all da planets out of recycled objects! it due 2morroeee i knoee this iss soo awesome! lolz! i be on 2morrow 2 let u know how it goes!

  41. Clifford says:

    Hi,

    Have a look at the date of the post (it is old, superseded news), and the content of the followup posts linking to it. Not to mention the explicit mention of updates in the body of the text.

    Best,

    -cvj

  42. catsrule says:

    We are doing a science report on the planets(the nine planets)and there’s actually twelve?Our book must be out of date.

  43. Clifford says:

    So what you’re saying is that you get the entire content of an article by reading only its title? Please see my comment immediately preceding yours.

    Thanks.

    -cvj

  44. Neha says:

    My Very Educated Mother Just Showed Us Nine Planets.

  45. Aurogra says:

    Wasn’t pluto’s downgraded because of its size and weak gravitational pull meaning its orbit has not been cleared? Meaning it is no longer a planet?

  46. Clifford says:

    Hi,

    Well, all over the post are things saying “update”, with supplementary information.

    -cvj