Why we still care about Pluto, the little non-planet
by Gordon Campbell
Pluto, the picked on planet. Always was the odd one out, routinely treated as the runt of the litter, even before it was kicked out of the club of planets altogether in 2006, thanks to a controversial vote held by the International Astronomical Union – at a meeting in Prague, no less. Yet Pluto, so small, so cold, so faraway still inspires an irrational level of protective affection. Kids supposedly like it because it is small, and prone to being bullied. New Zealand, for its part, took a somewhat sceptical stance towards Pluto, right from the start.
On March 14, 1930, Wellington’s Evening Post newspaper ended its one paragraph report on the finding of the new planet with a description bound to delight any child who has ever giggled over the name of the solar system’s seventh planet :
It is probably larger than the Earth, but smaller than Uranus.
Things barely improved when the Evening Post revisited the issue a week later in a March 22, 1930 report headlined A New Planet? All things considered, the Post was inclined to think the whole announcement might have been a mistake, a case of over-excited Americans jumping the gun:
These questions give plausibility to the suggestion made by Dr C.E. Adams, the New Zealand Government astronomer, namely: the possibility of an American newspaperman having overheard astronomers expressing the hope that the new planet was a reality. Through a mistake on his part, the new planet may have been announced as a fact.
Even if the Americans had got it right, the Evening Post wasn’t feeling all that impressed. Clearly, brash American money was now taking over science, just as in every other walk of life :
Whether the Americans have come as near to making a corner in minor planets as they have in First Folios of Shakespeare we cannot say, but it is only natural that with their magnificently equipped and magnificently placed observatories they should be able to claim a lion’s share.
By May of 1930, the matter of the discovery was settled and a name for the new planet had been chosen and announced. It would be called Pluto, god of the underworld and fittingly, the brother of Jupiter and Neptune. Perversely, the Evening Post gave the news of the naming scant coverage, and devoted many, many more columns instead (Evening Post, May 27,1930) to the likely repercussions for the people who believe in horoscopes :
..Mrs Elizabeth Aldrich, editor of “The Astrologer” writes that Planet X will enable her to step up her accuracy from 75% to 85%…There are two schools of thought among astrologers. One contends that the planet has always been exerting an influence, for good or evil, on mankind. The other holds that a planet remains absolutely neutral or harmless until it has been discovered, whereupon it begins to operate. This school does not indicate the means by which the planet is advised of its having been ‘spotted’ on Earth.
Among astrologers, the Post concluded, there existed some “mild disagreement” as to the identity of the new entrant.
“Evangeline Adams says it is known as Isis, the Rev. Arthur W. Brooks says its name is Vulcan or Lilith, Mrs Aldrich calls it The Great Unknown, and Jacob Levie refers to it as The Invisible.”
Supposedly, the name “Pluto” was suggested by an eleven year old English schoolgirl called Venetia Burney (left), who told her grandfather who told his friend an Oxford professor of astronomy who relayed the suggestion to the staff at Lowell Observatory at Flagstaff, Arizona who had made the initial discovery. Little Venetia made for a good p.r. angle but this was not the entire truth. Minerva had been the first choice, until it turned out to have been used already, on an asteroid. The astronomer and one-time Lowell employee Thomas Jefferson Jackson See came up with the popular name of Cronus, the son of Uranus – but since his former colleagues disliked See intensely, his suggestion went into the dustbin of history.
Pluto was a popular choice with the public, too. Its main downside in 1930 was that many Americans back associated it with the name of a popular and fast-acting laxative, marketed via the memorable jingle “ If Nature Can’t, Pluto Will.” It eventually won the day, although Miss Burney was not the only source of the name entirely. As this research into the suggestions tht poured into the Lowell Observatory indicates, plenty of others had offered the same name as well, but the story of the eleven year old English girl coming up with the name over breakfast tea and toast was too good to ignore.
By Pluto or any other name, this was an American planet, the first to be found and named by scientists in the New World. For a long time, astronomers had long been looking for a (bigger) planet beyond Neptune, until Pluto was discovered on the night of February 18, 1930 by a 22 year old former farm boy from Kansas, called Clyde W.Tombaugh. The telltale moving dot of planetary light had been detected by Tombaugh as he worked his way through a laborious comparison of a series of the Lowell Observatory’s star field photographs, in a patch of sky roughly in accord with computations made years before by the Observatory’s flamboyant founder Percival Lowell, who – as the Evening Post sceptically pointed out – had formerly been a champion of the existence of canals on Mars. (Tombaugh himself went on to have a long and distinguished career in astronomy, and died in 1997.)
Pluto became a pop cultural sensation in the 1930s. Walt Disney re-named Mickey Mouse’s cartoon dog ( until then it was called Rover or Pal) after the planet. The horror writer H.P. Lovecraft (pictured left) based the city of Yuggoth in his 1930 short story “ The Whisperer in Darkness” on Pluto, and it didn’t sound all that nice a place :
Yuggoth… is a strange dark orb at the very rim of our solar system… There are mighty cities on Yuggoth—great tiers of terraced towers built of black stone… The sun shines there no brighter than a star, but the beings need no light. They have other subtler senses, and put no windows in their great houses and temples… The black rivers of pitch that flow under those mysterious cyclopean bridges—things built by some elder race extinct and forgotten before the beings came to Yuggoth from the ultimate voids—ought to be enough to make any man a Dante or Poe, if he can keep sane long enough to tell what he has seen…
As Lovecraft fans will know, Yuggoth/Pluto was the home of the extra-terrestial Mi-Go, who dwell on the edge of a pit inhabited by a very, very old and even nastier cannibal thingy called Cxaxukluth…but that’s another story. In his youth, Lovecraft had been an astronomy buff. Just after his sixteenth birthday, he wrote a prescient letter to the Scientific American magazine urging the need for more astronomical effort and research in the region where Pluto lay waiting for discovery. Young Lovecraft’s letter in 1906 had begun :
In these days of large telescopes and modern astronomical methods, it seems strange that no vigorous efforts are being made to discover planets beyond the orbit of Neptune, which is now considered the outermost limit of the solar system…..
A quite different sort of Pluto-related horror story began to unfold later in the 1930s. Atomic scientists called a newly discovered element – plutonium – after Pluto, just as a previous generation of physicists had named uranium after Uranus. The atomic bomb dropped on Nagasaki in 1945 was in fact, a plutonium-triggered bomb,
This sense of the special American-ness of Pluto may explain the distress when Pluto was relegated to minor planet status in 2006. One of the final triggers for that action had been the discovery by the astronomer Mike Brown of Eris, another icy planet-like entity orbiting out beyond Pluto in a region that has come to be called the Kuiper Belt. Several other planet-like entities have also been discovered in the same region. (Though initially thought to be bigger than Pluto, Eris has recently been found to be almost exactly the same size.)
The upshot being – the population of the solar system suddenly looked likely to explode, if all these objects found out beyond Neptune were to be included. It was the same dilemma that had threatened to erupt after the first asteroids were located between Mars and Jupiter in the early 1800s. Then as now, the solar system club just couldn’t handle letting in all the likely applicants.
Just as Ceres, the biggest asteroid, became the head of a new sub-category in the 19th century, so Pluto has today become the king of a new category of sub-planetary objects out beyond Neptune. The re-classification of Pluto quickly became the butt of a million jokes. Brian O’Neill, in a column in the Pittsburgh Post-Gazette, used the demotion of Pluto to satirise the language of corporate down-sizing, starting with Pluto being called into the office to be told the bad news :
“Well, Ploot — I think I can call you ‘Ploot’ — we’re going to make some changes in the solar system, and you’re going to be a big part of them. A bunch of us in the International Astronomical Union got together and decided that, well, you’re too special to be associated with the likes of Mercury and Mars.’ You’re a still a planet, Ploot. Absolutely. But, as you say yourself, you’re pretty out there. A bit on the small side, too — not that there’s anything wrong with that. That’s why we’re making you chief of the plutons.”
Pluto : “I can’t believe you’re doing this to me only 76 years after you discovered me. I’m not a third of the way through my first orbit with you guys and you’re dumping me. Tell me what being the most famous member of the plutons means. It sounds a bit like being voted best Yugo at the auto show.”
“No, it’s not like that at all. Plutons are going to be very big. Kind of like Celestial Body Lite: Everything you always wanted in a planet. And less. You’re still part of the team, just not one of the classic planets anymore. No big deal. Look, Ploot, we recognized you’re upset, but this is really just a lateral move, not a demotion. You’re still a very important part of our solar system, and we’re looking at other objects about your size that we may make part of your team.”
Pluto : (Sniff) “I’m listening.” (Sniff)
“Hey, don’t go changing your climate over this, Ploot. As Owen Gingerich, the Harvard University man who chaired our panel, said, “We might be demoting it from the list of eight classical planets, but we’re promoting it by making it the head of its own special class.”
Not everyone took the relegation message lying down. The New Mexico state legislature for instance, quickly enacted a law that declared Pluto to be a planet, at least while it is passing over New Mexico. The full text of the New Mexico Pluto law is available here.
In similar vein, the California state legislature passed California Assembly Bill HR36, “Relative to Pluto’s Planetary Status” with its full text available here.
Among other things, the California law includes such clauses as
WHEREAS, Pluto was discovered in 1930 by an American, Clyde Tombaugh, at the Lowell Observatory in Arizona, and this discovery resulted in millions of Californians being taught that Pluto was the ninth planet in the solar system; and
WHEREAS, Pluto, named after the Roman God of the underworld and affectionately sharing the name of California’s most famous animated dog, has a special connection to California history and culture; and
WHEREAS, Downgrading Pluto’s status will cause psychological harm to some Californians who question their place in the universe and worry about the instability of universal constants; and
WHEREAS, The deletion of Pluto as a planet renders millions of text books, museum displays, and children’s refrigerator art projects obsolete, and represents a substantial unfunded mandate that must be paid by dwindling Proposition 98 education funds, thereby harming California’s children and widening its budget deficits…therefore be it
Resolved by the Assembly of the State of California, That the Assembly hereby condemns the International Astronomical Union’s decision to strip Pluto of its planetary status for its tremendous impact on the people of California and the state’s long term fiscal health..
Others used art to express their dismay. The singer/songwriter Jonathan Coulton for instance, wrote a poignant song called “I’m Your Moon” dedicated to the demoted planet, as told from the sympathetic viewpoint of Charon, Pluto’s companion moon. It includes this touching verse :
Sad excuse for a sunrise / It’s so cold out here
Ice and silence and dark skies /As we go round another year
Let them think what they like, we’re fine
I will always be right here next to you
Chorus : I’m your moon /You’re my moon
We go round and round /from out here, it’s the rest of the world that looks so small
Promise me /You will always remember who you are….
The duo of Jeff Mondak and Alex Stangl took a more direct approach on their “Pluto’s Not A Planet Anymore”
Since 1930, quite a run/ It was always the smallest one,
And oh so distant from the sun/But Pluto’s not a planet anymore
Listen James and Janet /Some experts said to can it
Now Pluto’s not a planet/No, Pluto’s not a planet anymore…
They met in Prague and voted /Now Pluto’s been demoted
Oh, Pluto’s not a planet anymore….
Not every scientist bought into the idea of demotion, either. Only 4 % of the world’s estimated number of professional astrophysicists had voted in Prague, as Pluto lovers never tire of pointing out. (Although as Neil DeGrasse Tyson pointed out in his book The Pluto Files, that’s still a statistically significant sample, provided it was sufficiently randomised.) Possibly, the final vote in Prague might have carried more gravitas if the visual aids up onstage had been a bit more…sophisticated. Reportedly, there was a beach umbrella on the podium with the word “planets” written on it, a big blue balloon represented the classical eight-planet solar system, a Disney dog soft toy stood in for Pluto, and a box of Cereal Crunch represented the asteroid, Ceres. Ultimately, only 91 holdouts among the assembled crowd of astrophysicists voted to put the cereal box and the soft toy underneath the umbrella.
As always, it came down to the classification criteria. Sure, Pluto is small, and its orbit is eccentric but even so…a dwarf planet is still a planet, right? Just as a dwarf person is still a person. Relatively speaking, as the science writer Alan Boyle says, our sun is a dwarf star. But it is still a star – and ditto for galaxies, big or small. From the viewpoint of Jupiter and the other gas giants, the solar system would probably look like a bunch of rocky dwarf planets closer to the sun and another bunch of icy dwarfs out beyond Neptune, with neither group looking like they had much in common with the big guys. Or, as the astronomer Alan Stern put it :
In fact, Pluto, and its cohorts, are planets. They have all the attributes of planets. Let me give you some examples. They have cores. They have geology. They have seasons and atmospheres. They have clouds. They have polar caps in many cases. They have moons. And I can’t think of a single distinguishing characteristic that would set apart Pluto and other things that you’d call a planet, other than its size. So, I like to say, a Chihuahua is still a dog.
What the IAU used to kick out Pluto were its chosen three criteria for planethood, namely :
1. The object must be in orbit around the Sun.
2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3. It must have ‘cleared the neighbourhood’ around its orbit. i.e it must dominate all other objects on its orbital path.
That third condition is the contentious one. Arguably, even Jupiter hasn’t cleared its neighbourhood, given how many asteroids trail before and aft, along its orbital path. Many entities cross over Neptune’s orbit, including Pluto, which has clearly worked out an accommodation with it. The condition of ‘clearing the neighbourhood’ can be a fairly subjective term. And if you picked a different criterion – such as, does it have a moon in orbit around it ? – then Pluto wins the contest hands down. Pluto and its three moons clearly outrank not only Mercury and Venus ( both none) but also Earth (one) and Mars (two). Yay for Pluto.
Finally- and to be optimistic about it – the case of Pluto is a useful reminder that any scientific classification system is, at base, pretty arbitrary. (When it comes to Venus for instance, the IAU’s naming committee decrees that any apertures more than 12 miles wide can be named after famous women, but smaller ones must only be given feminine first names. Go figure.) Truth is, a lot of people grew up with the idea that the solar system consisted of the Sun, nine orbiting planets, a belt of asteroids and the occasional wandering comet. It has been hard for some to adapt to a new vision of the solar system where Pluto isn’t a planet anymore, but is now – at best – merely the prime dwarf planet among many others like it.
Or is it a plutoid, or a pluton or whatever you want to call these things beyond Neptune ? Or is Pluto best considered as one of several Trans-Neptunian Objects, given that its eccentric orbit carries it at times closer to the sun than the orbit of Neptune ? Even weirder, maybe Pluto should be classed as a “scattered disc” like Eris, one of several entities affected by the gravitational force of Neptune, and the other gas giants. Or should Pluto be best considered as being a mere visitor from the Kuiper Belt, that recently discovered spooky neighbourhood of assorted planetary entities out beyond the solar system? Or is Pluto really a creature from the even more distant Oort Cloud of wandering comets, that also seem to swing in long, slingshot orbits around our sun?
Clearly then, the demotion of Pluto hasn’t returned us to a safe and secure set of the eight pre-1930 classical planets. Things will never be the same, especially as the Kuiper Belt and the Oort Cloud gradually reveal their secrets. Perhaps – as Tyson suggests – the varied contents of the solar system can be sliced demographically any which way you like, depending on your field of interest.
Understanding Pluto leads us forward to a view of a porous solar system where things overlap at the boundaries in ways we are only beginning to understand. Meanwhile, our protective feelings towards Pluto are very likely to endure. This icy little whatsit isn’t going anywhere, fast. Come 2015, when the New Horizons space probe finally reaches Pluto and heads into the Kuiper Belt, Clyde Tombaugh’s baby can count on enjoying yet another spell in the news spotlight.