Happy 80th Birthday, Pluto!

We used to think Pluto was a misfit. -Alan Stern

Eighty years ago, we solidly had eight planets in the Solar System: the same eight we have now.

But in the late 1920s, a young astronomer was looking up at the sky, night after night, searching for tiny moving objects that could possibly be planets out beyond Neptune. Using this technique of looking at a patch of sky repeatedly over the course of a week, Clyde Tombaugh searched for moving objects, finding many comets and asteroids, but — like everyone else — found no signs of a new planet.

Until January of 1930. I’ve managed to dig up Clyde Tombaugh’s slides of those two fateful nights that led to the discovery of Pluto.

See where the white arrow is pointing? That’s what Clyde Tombaugh noticed. This faint, tiny object appeared to move, night after night, against the fixed background of stars. Very quickly, this discovery was announced and confirmed, and on February 18th, 1930 (four score and one day ago), it was declared that our Solar System has nine, and not eight planets!

Today, we know that Pluto is not some long-lost frozen world out beyond the gas giants, but rather the first object ever discovered in the Kuiper Belt, the largest structure in our Solar System consisting of thousands upon thousands of tiny frozen worlds, ranging in size from little comets to huge, Moon-sized worlds!

The IAU may tell us that Pluto isn’t a planet anymore, but don’t let a small group of scientists tell you what is and isn’t of great importance in our Solar System. Pluto was the only known Kuiper Belt object for 48 years, and do you know what the second one discovered was?

Charon, Pluto’s giant Moon! (As imaged here by the Hubble Space telescope, and shown along with Pluto.) We didn’t discover a third one until the 1990s, and now we have a deep-space probe on its way to Pluto to roam among the Kuiper Belt, for the sole purpose of scientific exploration.

So happy 80th birthday, Pluto. I may be in the scientific minority, but I still think of you as a giant in our Solar System, and as the ninth classic planet.

Comments

  1. #1 Markk
    February 19, 2010

    So what do you consider Eris? It’s bigger and more massive than Pluto. The first modern planet?

  2. #2 llewelly
    February 19, 2010

    Eris is a KBO, and a dwarf planet, just like Pluto.

  3. #3 Pierce R. Butler
    February 19, 2010

    I’ve seen it claimed that, in his prolonged search for Planet IX, Clyde Tombaugh became the human being who has looked at more stars than anyone else.

    Since such functions are now computerized, the claim went on, Tombaugh seems likely to hold that record for all time.

  4. #4 MadScientist
    February 19, 2010

    Good ol’ blink comparators – they’re great for finding stuff (too good if you’re looking at 2 scenes with substantial differences). These days we just let computers do the job of finding changes; no more straining those human eyes.

  5. #5 Douglas Watts
    February 19, 2010

    Great post, Ethan.

    Neptune was discovered on September 23, 1846. This meant almost 90 years passed between the discovery of the eighth and outermost planet and Tombaugh’s discovery of Pluto. The amount of determination and sheer hours Tombaugh spent to find Pluto made the story of Pluto’s discovery compelling to me as a kid, esp. since no other planet had been discovered in the half century from 1930 to the 1980s. The story of Pluto’s discovery by one lone, determined guy in a very cold observatory night after night is part of what first got me interested in astronomy.

  6. #6 johnR
    February 20, 2010

    “… this discovery was announced and confirmed, and on February 18th, 1930 (four score and one day ago), it was declared that our Solar System has nine, and not eight planets!”

    Didn’t they delay the announcement until Percival Lowell’s birthday in March?
    Nice post!

  7. #7 Vagueofgodalming
    February 21, 2010

    The IAU may tell us that Pluto isn’t a planet anymore, but don’t let a small group of scientists tell you what is and isn’t of great importance in our Solar System.

    Indeed not.

    It must take a remarkably muddled mind to equate ‘not considered to be a planet’ with ‘I must treat as less important’.

  8. #8 Laurel Kornfeld
    February 21, 2010

    Our solar system does NOT have only eight planets, and it is far more than a minority of scientists who still view Pluto as a planet and a Kuiper Belt Object. The same is true for Haumea, Makemake, and Eris. . Only four percent of the IAU voted on this, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. Stern and like-minded scientists favor a broader planet definition that includes any non-self-luminous spheroidal body in orbit around a star. The spherical part is important because objects become spherical when they attain a state known as hydrostatic equilibrium, meaning they are large enough for their own gravity to pull them into a round shape. This is a characteristic of planets and not of shapeless asteroids and Kuiper Belt Objects. Pluto meets this criterion and is therefore a planet. Under this definition, our solar system has 13 planets: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, and Eris.

  9. #9 lol
    February 22, 2010

    RIP PLUTO 1930-2006

    You will be missed

  10. #10 Hitesh
    February 22, 2010

    That’s a young planet. My impression is that planets were born millions if not billions of years ago.

    Happy Birthday. May you live have many more.

    :) <—-(Smiley face in case anyone takes my sarcasm too seriously)

  11. #11 Mark E.
    February 22, 2010

    Does anyone else realize that around 1830 there were 13 planets in the solar system?
    Anyone want to know WHY that was?… it was because astronomers were discovering the first few asteroids. The Kuiper belt of icy objects beyond Neptune is the late 20th century’s version of the Asteroid belt.
    They just didn’t have a cute dog to name the damn asteroids after in the early 1800s, so now Americans (& only Americans) are upset about it.
    Here is the largest of the planet-asteroids:
    http://en.wikipedia.org/wiki/Ceres_(asteroid)

  12. #12 DesertHedgehog
    February 22, 2010

    Happy Birthday, Ninth Planet! Pluto will always be a planet for me, whatever some cabal of Foreignji (probably intent on some ‘postcolonial’ project of diminishing the Western-described solar system) at the IAU may think. Pluto has that cool fused-PL symbol, and it was the subject of Don Wollheim’s “Secret of the Ninth Planet”, a favourite book of my Long-Ago Youth. And, for Lovecraft fans, Pluto will always be Yuggoth, home of the nightgaunts. Pluto also appeared in the forgotten proto-anime “Space Angel” back in the early Sixties. So— I’ll never give up Pluto as Planet IX! Happy birthday, little guy! (And your moon Charon, too!)

  13. #13 EK
    February 22, 2010

    @11
    The cartoon dog was named after the planet, not the other way around.

  14. #14 Laurel Kornfeld
    February 23, 2010

    No need to wish RIP for a planet that is very much alive.

    It is not only Americans who reject the IAU’s controversial demotion of Pluto. I have been running a blog advocating Pluto’s reinstatement for three-and-a-half years, and during that time, I have heard from people all over the world who oppose the demotion. A lot of these are people on astronomy forums or members of astronomy-related groups online, people who already have a strong interest in the solar system.

    The demotion of Ceres from planet to asteroid was actually a mistake. Nineteenth-century astronomers could not resolve Ceres into a disk, so they didn’t know that unlike almost all other objects in the asteroid belt, Ceres is round. This means it is large enough to be in hydrostatic equilibrium. The fact that it is spherical was not recognized until the late 19th century. Pallas and Vesta are questionable, as they appear to have been spherical and subsequently hit by asteroids that knocked part of them. Pluto and the other spherical KBOs are as unlike the majority of tiny, shapeless KBOs as Ceres is unlike the majority of asteroids in the belt between Mars and Jupiter. This means that both demotions, of Ceres, and of Pluto, were wrong.

    And why is it a problem if we have a large number of planets in the solar system? Isn’t a desire to artificially keep the number low a sentimental rather than a scientific argument?

  15. #15 FranColt91
    April 18, 2010

    I still have to get used to naming Pluto as the 9th planet. It has glued into my mind that Pluto was the 8th planet growing up after all these years. Funny how facts can be altered with scientific advancements and discoveries. I have to agree with the last message of this post though – Pluto may be one of the smallest galaxy structures but she will always be a giant cornerstone in the final frontier that we call space.

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  16. #16 annuity ratings
    April 19, 2010

    since i was in grade school i love my teacher when she was going to talk about universe, my mind starts to go on day dream that i was walking around each planet. Cool Science.

  17. #17 Abnehmen Tipps
    April 20, 2010

    Happy 80th Pluto! Who knows, maybe in another 8 years, more proof would be found that Pluto is indeed a planet and we’ll have 9 again!

  18. #18 Find Jobs
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    Ha, im sure pluto will not mind 80 years old!! i wonder if Clyde W. Tombaugh, the guy that found Pluto ever made it to the same age??

  19. #19 Ben10 games
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    “Ha, im sure pluto will not mind 80 years old!! i wonder if Clyde W. Tombaugh, the guy that found Pluto ever made it to the same age??” that is a good question, I wonder what the answer is.

  20. #20 GiaSimmons28
    April 21, 2010

    I can’t believe it’s Pluto’s 80th birthday. Having said this, the planet has yet to be visited by a spacecraft. We do know that the planet is mostly made up of ice which is one of the reasons it might be very difficult for any mission to take off.

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  21. #21 Frank
    April 23, 2010

    Its pluto’s 80th birthday, I guess I didn’t know that until I read this. I have done some research on the universe but never really looked into the age of the planets. Maybe I will look into that next. Thanks for letting me share.
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  22. Happy 80th Pluto! Who knows, Pluto may still evolve into a full grown planet someday!

  23. #23 The Woodlands Realtor
    April 24, 2010

    Wow, happy 80th. I’ve always wondered what kind of purpose Pluto plays. I wonder how much more we will now about the plants around us in the next 80 years.

  24. #24 luckytrader
    April 26, 2010

    The IAU may tell us that Pluto isn’t a planet anymore, but don’t let a small group of scientists tell you what is and isn’t of great importance in our Solar System. Pluto was the only known Kuiper Belt object for 48 years, and do you know what the second one discovered was?
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  25. #25 MBA Lady
    May 10, 2010

    The Woodlands Realtor,
    I think we should concentrate more on studying the Earth. There are plenty of mysteries here, not only in space. However it’s great the astronomy is moving forward.

  26. Happy Birthday Pluto! It’s not a planet anymore, but it’s still studied in fifth grade science class as if it were one still.

  27. #27 robert
    June 16, 2010

    Hi very true and totally koool, Theroys in and of Time are very beauftil so study and learn about. Time has no beggning and no end…..

  28. #28 Kathy20
    June 18, 2010

    I love studying outer space. This has been a interest for me for a very long time. I think Pluto is interesting because it is so far away from us. It amazing to think we know so much about this planet.

    Thanks Kathy Dilfer
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  29. #29 Dating Sites Schweiz
    July 5, 2010

    I never knew that Pluto was already 80! Too bad it lost its Planet status & was demoted to Dwarf Planet! Maybe Pluto would still have a chance to evolve into a planet some day!

  30. #30 Oak Furniture
    July 12, 2010

    Happy Birthday Pluto! You are the same age as my grandfather.

  31. #31 Schnell Abnehmen Tipps
    July 14, 2010

    Pluto used to be one of my favorite planets. Hopefully in another 8 or 80 years, it could evolve back into one, if its even possible.

  32. #32 ChannelBlu
    July 30, 2010

    Based on what I learn, Pluto should be one of my favorite Planet. Happy birthday!

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  33. Happy Birthday Pluto! :-)

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  35. #35 Flowers
    August 30, 2010

    The amount of determination and sheer hours Tombaugh spent to find Pluto made the story of Pluto’s discovery compelling to me as a kid, esp. since no other planet had been discovered in the half century from 1930 to the 1980s.Thanks for sharing this article with us. I am very happy to find your blog.

  36. #36 MikeC
    September 2, 2010

    Everybody misses the fact that by the new definition, Neptune isn’t a planet anymore either. It hasn’t ‘cleared the neighborhood of it’s orbit’….of pluto.

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  38. #38 Technology
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    So it is nice info. wanna say happi birthday to pluto
    Pluto is one of my favorite planets. Hopefully years, it could evolve back into one, if its even possible.

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  41. #41 CFD
    September 26, 2010

    Pluto will allways be my favourite planet. Happy birthday it is one of another million to come.

  42. #42 Dog Spray
    October 8, 2010

    Wow, happy 80th. I’ve always wondered what kind of purpose Pluto plays. I wonder how much more we will now about the plants around us in the next 80 years.

  43. It is interesting now that we have found out there could be life on another planet, but apparently we will never know for sure because we can’t make it that far in space.

  44. #44 Soffe shorts
    October 14, 2010

    I guess I don’t understand why Eris was never a planet in our Solar System?

  45. #45 Pink Ring
    October 18, 2010

    I can’t believe that guy was able to see that small dot. Mind you, I guess when it’s your job to review these kind of things you are probably a bit more thorough than the average person.

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  47. #47 Chris Marks
    October 25, 2010

    Pluto has not yet been visited by a spacecraft. A spacecraft called New Horizons was launched in January 2006. If all goes well it should reach Pluto in 2015.

    Happy Birthday Pluto!
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  56. #56 Oak Furniture
    December 3, 2010

    Pluto ,Happy birthday from side as well !!!! I hope you don’t mind being 80 as people older people are more wiser.I don’t want to drown in a discussion that you are a 9th or the 8th planet .The important thing for me is ,you are still up there and revolving as happily as you started 80 years ago.

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  58. #58 Gift baskets
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    I wonder why anyone still cares about pluto. It’s not even a planet!

  59. #59 stellenmarkt
    January 1, 2011

    So pluto got pushed off the planet list? I wonder if uranus or neptune is next?

  60. #60 theo
    January 10, 2011

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  61. #61 maopo
    January 15, 2011

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  62. #62 art lists
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    Well as guys above said it’s not even a planet anymore so why should we care?

  63. #63 Anthurium
    March 10, 2011

    I’m bummed that Pluto isn’t a planet anymore. I grew up thinking that we had 9 planets in the solar system. C’est la vie. – anthurium flowers

  64. I’m disappointed that we’ve lost Pluto as the 9th planet.

  65. #65 New Homes Blackpool
    March 17, 2011

    I still don’t understand why Pluto has been removed as the 9th planet. Who’s to say that Uranus won’t be next?

  66. #66 Joel Ong
    August 15, 2011

    Pluto, the last celestial mass in the solar system is not a planet really as pointed out recently. The nine planets that exist in the solar system still consists of nine planets excluding Pluto. Likely, there are more out there needs to be discovered.
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  67. #67 bushnell tour v2
    August 23, 2011

    Hi Ethan,

    I didn’t knew that Pluto is 80 years old until now. Really good info about it and the man who discovered it.

    Cheers!

  68. #68 eula angelie j. escanilla
    February 23, 2013

    i don’t know that pluto is 80 years old. this is the first time i discover it!!!!!!!!!!!!!!…………………

  69. #69 monica santos gabriel
    brgy. isla
    March 10, 2013

    i want to gratulate the pluto i want say in pluto happy 80 birthday

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