We used to think Pluto was a misfit. -Alan SternEighty 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.
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Comments
So what do you consider Eris? It's bigger and more massive than Pluto. The first modern planet?
Posted by: Markk | February 19, 2010 4:37 PM
Eris is a KBO, and a dwarf planet, just like Pluto.
Posted by: llewelly | February 19, 2010 4:42 PM
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.
Posted by: Pierce R. Butler | February 19, 2010 4:54 PM
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.
Posted by: MadScientist | February 19, 2010 7:48 PM
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.
Posted by: Douglas Watts | February 19, 2010 9:23 PM
"... 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!
Posted by: johnR | February 20, 2010 11:26 AM
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'.
Posted by: Vagueofgodalming | February 21, 2010 6:28 AM
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.
Posted by: Laurel Kornfeld | February 21, 2010 8:24 PM
RIP PLUTO 1930-2006
You will be missed
Posted by: lol | February 22, 2010 12:27 PM
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.
:)
Posted by: Hitesh | February 22, 2010 1:07 PM
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)
Posted by: Mark E. | February 22, 2010 1:09 PM
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!)
Posted by: DesertHedgehog | February 22, 2010 2:43 PM
@11
The cartoon dog was named after the planet, not the other way around.
Posted by: EK | February 22, 2010 5:37 PM
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?
Posted by: Laurel Kornfeld | February 23, 2010 1:09 AM
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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Posted by: FranColt91 | April 18, 2010 7:41 PM
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.
Posted by: annuity ratings | April 19, 2010 12:09 PM
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!
Posted by: Abnehmen Tipps | April 20, 2010 7:06 PM
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??
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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.
Posted by: Ben10 games | April 21, 2010 9:56 AM
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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Posted by: GiaSimmons28 | April 21, 2010 10:58 PM
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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Posted by: Frank | April 23, 2010 9:37 AM
Happy 80th Pluto! Who knows, Pluto may still evolve into a full grown planet someday!
Posted by: Fettverbrennungsofen Erfahrungen | April 23, 2010 7:25 PM
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.
Posted by: The Woodlands Realtor | April 24, 2010 11:19 AM
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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Posted by: luckytrader | April 26, 2010 8:35 AM
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.
Posted by: MBA Lady | May 10, 2010 8:37 AM
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.
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Posted by: robert | June 16, 2010 1:56 PM
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.
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Posted by: Kathy20 | June 18, 2010 9:27 PM
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!
Posted by: Dating Sites Schweiz | July 5, 2010 2:43 AM
Happy Birthday Pluto! You are the same age as my grandfather.
Posted by: Oak Furniture | July 12, 2010 9:50 PM
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.
Posted by: Schnell Abnehmen Tipps | July 14, 2010 4:45 PM
Based on what I learn, Pluto should be one of my favorite Planet. Happy birthday!
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Posted by: ChannelBlu | July 30, 2010 10:16 AM
Happy Birthday Pluto! :-)
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Posted by: sole f80 | August 17, 2010 9:48 AM
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.
Posted by: Flowers | August 30, 2010 6:04 AM
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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Pluto is one of my favorite planets. Hopefully years, it could evolve back into one, if its even possible.
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Pluto will allways be my favourite planet. Happy birthday it is one of another million to come.
Posted by: CFD | September 26, 2010 1:54 AM
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.
Posted by: Dog Spray | October 8, 2010 11:40 AM
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.
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I guess I don't understand why Eris was never a planet in our Solar System?
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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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Posted by: British Airways flights | October 23, 2010 7:16 AM
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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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.
Posted by: Oak Furniture | December 3, 2010 4:43 AM
Wow this is a pretty good but i thought pluto is not a planet anymore..
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I wonder why anyone still cares about pluto. It's not even a planet!
Posted by: Gift baskets | December 24, 2010 2:12 PM
So pluto got pushed off the planet list? I wonder if uranus or neptune is next?
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Posted by: maopo | January 15, 2011 4:24 AM
Well as guys above said it's not even a planet anymore so why should we care?
Posted by: art lists | February 26, 2011 5:23 PM
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Posted by: Anthurium | March 10, 2011 8:42 PM
I'm disappointed that we've lost Pluto as the 9th planet.
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I still don't understand why Pluto has been removed as the 9th planet. Who's to say that Uranus won't be next?
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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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Posted by: Joel Ong | August 15, 2011 5:38 PM
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!
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