Why is Pluto Not a Planet?

pluto.jpgIn August of 2006 Pluto was declared to no longer be a planet. This was due to a rewriting of the definition of “planet”.

According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit.

Pluto has been demoted because it does not dominate its neighborhood. Charon, its large “moon,” is only about half the size of Pluto, while all the true planets are far larger than their moons.

Pluto is now officially a “dwarf planet”. But it’s no longer part of an exclusive club, since there are more than 40 of these dwarfs, including the large asteroid Ceres and 2003 UB313, nicknamed Xena—a distant object slightly larger than Pluto discovered by Brown last year.


Update Feb 2009: You can talk about this topic in the discussion forum at (and play video games too!):

Update May 2009: Here is information about the “Planet X” theory and information on why Pluto was initially considered a planet: http://en.wikipedia.org/wiki/Planet_x

Update August 25 2009:
The debate rages on. Did you know that 90% of the critical letters complaining about Pluto’s demotion come from North America? Food for thought, here’s the article:

132 thoughts on “Why is Pluto Not a Planet?

  1. i think pluto isnt a planet coz it haz ice and stuff on it. does any one here like chocolate coz i do……….

  2. i like chocolate 2 and pluto isn’t a planet cos there are at least 70 000 other planets the same size as pluto in the kuiper belt so really its just another kuiper belt object

  3. i like chocolate 2 and pluto isn’t a planet cos there are at least 70 000 other planets the same size as pluto in the kuiper belt so really its just another kuiper belt object

  4. Hey this is Rosalia and whated to say that pluto isn’t a planet bcause it is covered with ice and otherthings i don’t know so this is what i just wanted to say this becaues i think i am really smart but in my family evreyone thinks i’m STUIP which i am not so this is what i wanted to say about pluto that it is covered with lots of ice and it is not considered a plante anymore so there you have it!!!


  6. PLUTO is not a planet,but its far better to be a Dwarf PLANET,and there are hundreds of Dwarf PLANETS in the solar system which does not resemble PLANETS.Therefore PLUTO has no question of becoming a PLANET.

  7. i think Pluto is nOt bEcAUsE it iS the FARtHEsT plANeT In thE SOLar SysTEM aH bzta pra saken d Xa plANeT i h8 nThaT PlANet so MuCh!!!

  8. PLOUTO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    I LOVE YOU PLOUTO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!CHOCOLATE


  9. hi!i say that pluto is no more a planet coz there is no life in pluto and if scientist will agree that pluto is a planet they will have to allow the asteriods which are as same size as pluto which is impossible because they are more than 40 asteriods so if they allow pluto to be a planet they will have to allow 40 asreriods to be a planet and pluto has no life coz it’s too cold there that if someone wiil go in that planet he/she will freeze that is what i wanted to say tanxs

  10. hi! pluto is ma best planet and wen i heard dat pluto is not a planet i was so dissapointed i luvvvv pluto it is da besttttt!!!!!!!!!!!!

  11. hi! i say that pluto is no more a planet coz it is a big ball of ice and it was the ninth planet of solar system and it does not fit in with the pattern of the other planets

  12. Pluto can’t be a planet…. it’s a dog!!!!!!!!!!!!!!Forget chocolate, how about Nutella 🙂

  13. i am researching why pluto is not a planet… well, first, it has not “cleared its neighborhood” of its orbit…but,those other laws, pluto did pass it… i think pluto should be a planet… i guess we will have to settle it as a dwarf planet…:(

  14. i think pluto shoulf be a planet because its been one for the longest and it shouldnt matter wat the definition sats cuz to me pluto is a still a planet no matter wat no one says

  15. no 1 cares wether or not pluto is a planet!!!!!!!!!!!!!!!!!! and only cool kids can like chocolate and u guys r not cool!!!!!!! ur nerds:(

  16. i am very sad that pluto is not a planet and what is up with the chocolate bussines

  17. pluto is a grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrreat planet although it is not anymore

  18. i hate science and i love chocolate like helllllllllllll

    y r we sopposed to go to skool if we dont attend claasses that wat i do

    see ya every1:)

  19. I think PLUTO is a planet because its in the solar system and I LOVE SNOW .I think all the people who said and made PLUTO not a planet to retern our pluto a planet even if it is different from the others .We are different too!

  20. Ok Pluto will always be a planet in my books. But techniqelly with all the scientist facts about what defines a planet Pluto misses out on one of these. And if scientiest did decide to let Pluto be a planet they would have to let approx 40 ‘planets’ into our solar system which would totally suck. With PLutos compositions and everything Pluto is just another object in the Kuiper Belt. But for many years before PLuto was discovered, scientist believed that there would be a ninth planet in the solar system, so what changed their mind to not let Pluto be one? ARRR it anoys me but im sorry to say Pluto is not a PLanet but a dwarf planet, but PLuto will always be a planet to me.

    And guys seriously chocolate? how the hell do you get from space to chocolate? i know it is awesomely awesome, but seriously?

  21. Pluto is smaller than any other planet, even smaller than Eath’s moon. Its dense and rocky. Pluto’s orbit is erratic. One of its moons, Charon, is about half Pluto’s size! Its now officially a “dwarf planet” and officially not considered a planet.

  22. Pluto should be considered a planet because it has been a planet since 1930 and just because so scientist wants to change the definition its a dwarf now. You guys are racist

  23. How is it that you can just change a definition to define what is considered a planet and what isn’t?

  24. Because under the old definition of a “planet” – and the discovery of new objects – we would end up with many many nearby “planets” – which is just confusing for everyone. So they redid the definition of a planet to keep the local number manageable. That’s a simplified explanation.

  25. pluto is i snt a planent coz its a silly fakin planet ok any one like ice lollyes coz i do….

  26. Why in the world cant pluto be a planet????? im doing a project on pluto and just because it is covered in ice doesnt mean that pluto isnt a “planet”. it has a moons just like the other “planets”. it even orbits the sun! but now scientists say that pluto came from another galaxy and that it just got stuck in orbit around the sun. poor pluto is now a “dwarf” planet…. ~niki b.~



    Pluto Isnt a planet Because its moon Charon is Half the size of pluto. so it is not a planet..


  29. I dont think that pluto is a planet cuz it is to far away from the sun and it is WWWWAAAAAYYYY TO small!!!!!-But i like its name

  30. Pluto is 2 small and itz got ice and is 2 far from da sun itz sum tiny planet innit who lykz fifa o9 bang bang

  31. alright guys, Pluto is no longer a planet because the IAU changed the definition of “planet”. A planet is the following:
    1. An object that orbits the sun. It can not be orbiting any other object.
    2. Be a sphere- must have enough gravity to smooth itself out (major bumps and ridges)
    3. Clears its orbital neighborhood- No other bodies in its orbit. Should sweep up all debris in its orbit (except for moons, since they are gravitationally caught).

    The IAU did NOT look out to simply stripe Pluto of its planetary status, they simply redefined “planet”, and Pluto just so happen to fail at the third requirement as listed above. It is not because it is too small, it just needs to meet requirements, none of which specify a certain size a planet must be. If it were categorized as such, it would simply be science by convenience.

    I hope this cleared some things up.

    I love chocolate too XP

  32. WHY DOES EVERYONE CARE SO MUCH ABOUT THIS GIANT SNOWBALL IF SCIENTISTS SAY ITS NOT A PLANET THEN ITS NOT A PLANET now if it was a giant chocolate ball or something then it should be considered a planet but it isn’t so it’s not.


  33. pluto is not a planet, i think cuz it’s a dwarf……????i think…????im confused….:{….?????

  34. im hot ur not lolx……dnt u wish ur girlfren was hott lyke meh….lmao…:)……..

    oh yea were suppose to be talk’n bout dhat planet…..its a dwarf rite….??????


  36. you guys are rong pluto is not aplanet for some stupid reason but i am ten years old and i am studing in school about this so i think i was made to not be a planet makayla

  37. and jayzee i wouldnt use words like that around kids because i now what that says because my dad does it all the time makayla to Jayzee

  38. can you just tell me if pluto is a planet or not.
    and all these lil kids leavin stupid comments,
    your really immature and you needa get a lifee if you
    dont care about this then dont go on this website and read all the stufff. ohhkk.
    -bee breeezzyyy ;]

  39. guys Pluto is a planet.
    just because Pluto doesn’t have a clear neighborhood shouldn’t classify it as a planet. i think if that’s the case than Neptune should not be classified as a planet either. because Pluto orbits overlaps Neptune orbits making Neptune not have a clear neighborhood. so if that’s really the case then Neptune should not be a planet either. therefore Pluto should be considered a planet as well. lastly i don’t think that it is right to classify a planet with such little qualification when talking about something this major. so we wont have to second guess and regulate the rules in order for something to be or not to be a planet. also for it would not cost so much to buy new text books!!! but then again I’m no scientist
    [a 9th graders opinion]

  40. Pluto should be considered a planet. It has always been considered a planet, until 2006. Nothing has drastically changed about Pluto and it does cross orbit Neptune. The only thing that has changes is the homosapian definition of what makes a planet.

    People can never leave anything alone, but constantly change what works to fit their discoveries. I hope they made great $ to change the definition and finally make a new discovery that Pluto is actually classified as a dwarf planet…. WTF is a dwarf planet. A planet is a planet is a planet. Dwarf… BULLSHIT that’s what it is. So now this PLANET is considered to be part of the Kuiper belt… a belt/home of comets. Redunkulous!!!!!!!!

  41. Science will always be changing when new evidence presents itself. The discoveries of space are continuing. If Pluto were defined as a planet – then there are also hundreds of others that would now have to be called planets. So the choice was to either include those hundreds of others as planets, or redefine Pluto as not being a planet.

    Adding hundreds of planets to the records overnight was a little much to handle, so they chose to redefine Pluto.

  42. im sooooooooooooooooooooo sad tht pluto isnt a planet anymore because its interesting to learn about the plant pluto…
    it has alot of memmories tht are not goin 2 be left behind!!!!!!!!!

  43. 😀 hi i am doing a project on space, and i have to write about why pluto is not a planet anymore and this website gave me a pageful of facts for it, and people who are swearing and stuff dont listen because i quite like this website and the picture is cute

  44. Not fair! I have to Say to my 11 year old I he is right and me Wrong! I still just don’t get why Pluto had to get kicked out of the club and to find my Son is smarter then me! So not right!

  45. am so sad that ploto is not a planet. i love this planet alot
    i want to cry my tears is coming out when i read that ploto is not a planet any more………i will miss u ploto

  46. I think itz not a planet becuz itz 2 small

    P.S.You gize like chocalet way 2 much!!!!!!!!!!!!!!!!!!!!!!!!!

    love yours trully ROD$$$$$$$$$$$$$$$$$

  47. pluto is a planet and it’s still hear ok. And it’s not stupid i love pluto .And choclate is to sugary I hate it.And yall are gone to be jumpping like some monkeys.

  48. Pluto should’nt be a planet because it’s in as one of the Kuiper Belt objects. I think Eris (2003UB313) should be the 9th planet instead of Pluto, because it’s bigger.

    @Dudley Puppy… No, Pluto is not a “Meateore”, if it was it would be non-spyrical. PS. learn how to spell.

    @jericca… Geez it’s just a planet. It’s not going anywhere…

    @Anonymous… Learn how to spell.

  49. poor pluto. i dont like it that pluto isn’t a planet because it is so small

  50. Wow, umm… I just can’t believe that pluto isn’t a planet anymore… I mean, WHAT’S WRONG WITH THE SCIENTISTS THESE DAYS?! But I mean, they do have a point tho… so yeahhh
    I LOVE CHOCOLATE! How about you?

  51. now right yall see tht pic up there it say poor pluto i feel sad bout him he look like a lil babe rebaccea we dont care if you love iny thing

  52. Pluto is a planet, Duhhhh? just because it’s small, it doesn’t mean it’s not. >PLUTO’S A PLANET< and I don't give a @*9&@#$^!

  53. so beause my saname is radinku and i

    love pluto is my friend i have 12 yar sorrrrrrrrrrrrrrrrry pluto but u pluto u are adwarf broo u are nomo planet u a fakin

  54. Pluto’s total mass is smaller than the total mass of objects around it. It has nothing to do that it’s a big rock or it’s covered in ice. Neptune and Uranus are made of ice. That’s why Pluto isn’t a planet

  55. I have no opinion of weather Pluto is a planet or not . But yall dont make sense . Pluto has been a planet for over 70 yrs & yall aqreed to that this whole time.. but now all a sudden researchers chanqe their opinion so now yall think your smart cause you know weather it is . But if yall really thouqht that Pluto wasnt a planet, then why didnt yall say anythinq

  56. jericca u 1 stupid dude its PLUTO, PLUTO!!!!!!!!! like ur sad because a planets not 1 enymore U ALSO SOOO SADDDDD

  57. Funny, I bet that scientists argued the same way over “is the world flat or round?”, “is atom the smallest particle of an element?” or “was Michael Jackson’s skin white, because of bleaching or illness?”. In the end the last questions was the most interesting one.
    Friends, we have reached a new stage in our “Entertainment Era”, where all the great celebrities die and be replaced by celebrities that are famous because of scandals, sex tapes and/or bad character. It’s the time of this Entertainment Era that the more intelligent youth completely turns its attention to more trivial matter – politics (which were shaped by the death of billions), economy (which is important for your present well being), galaxy (which is important for our future generation).

    One cannot say what is Pluto, because not all facts are known. We will know the answer in 2015, so move along, nothing to see here!

  58. I really don’t like that Pluto isn’t a planet any more, but some people just have to deal with it.

  59. u people r crazy just leave the poor planet alone or we r not ganna do a new epersode of Shake it up u bum heads! peace out

  60. Pluto should be a planet because planets need to:
    * orbit the sun
    * have enough gravity to keep shape
    * clear other things around it
    but, if that’s so is mars cant be a planet???

    I <3 a good amount of chocolate

  61. Whahahahaheeheeheehee! Just found the following quote on the net:

    “Somebody Tried To Tell Me There Was 50 States In America. Nuh Uh Cause The Scientists Found Out
    That Pluto Dont Exist. We Got 49 Dumbass.”

  62. Pluto is not a Planet. Because, It doesn’t clear its orbit around it. It’s just a random kuiper belt object. But, They should make poor pluto a planet again.

  63. If a human was born small, had disabilites, and was very weak would it be considered a human if not then we have no risen to say Pluto is not a planet

  64. Hello Anonymous,
    Wonderful insights. Two thoughts on this. First of all, although I am certainly no scientist, my understanding is that Pluto was not denied “planet status” directly because of its size, but because of its gravitational field or its non-affect on other bodies (something like that). Second thought is that I should install spell-check on my blog.

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