Clyde Tombaugh was just 24 when he made his biggest discovery. The year was 1930, and the fact is Clyde was actually looking for something else when he first sighted Pluto, which makes it a mistaken coincidence that he found his little planet at all. At the time Clyde was immediately wrong about Pluto’s significance, and the rest of the world became mistaken with him. Clyde and Pluto are a fine example of how the order of things consistently conspires to make our wrong turns wonderful in the outcome all the same.
To fully appreciate the story of Clyde and Pluto, we’d have to first look back at the discoveries of Uranus and Neptune. Our solar system’s seventh planet Uranus was spotted in 1781 by English astronomer William Herschel, who initially mistook the dot in the sky to be a ‘moving star’, or more likely a comet. Uranus is a long way out there, and Herschel was the first ever to discover a planet by means of telescope, instead of the unaided eye. It took another two years before a second astronomer, Johann Bode in Berlin, figured out that Herschel’s object was indeed a new planet.
About 60 years after that, French astronomer and mathematician Urbain Le Verrier rather ambitiously decided to combine and harmonize all the published mathematical models predicting planetary movements within the solar system into a single work. In the course of applying his and others’ calculations to direct observation, Le Verrier noticed some slight but regular variations in the orbit of Uranus. A stickler for detail (obviously…), he spent months working on the phenomenon until at the end of August, 1846, Le Verrier announced his prediction that there must be another planet out there responsible for the effect on Uranus. And by September 18, he was mailing a predicted position for the planet to the Berlin Observatory. When they received his letter five days later, they took a look and found Neptune that same night, within 1 degree of where Le Verrier had described it should be. Le Verrier had found another new planet, and without the telescope, or even the naked eye — his discovery had been made by his written hand applied to paper.
So it seemed that the source of gravity yanking on Uranus’s orbit had become apparent, but questions yet prevailed. The gravitational physics still didn’t add up and speculation began that there must be yet another body out there influencing Uranus and, come to look at it, also the new planet Neptune.
Enter Percival Lowell, a wealthy renaissance man trained in mathematics at Harvard who, toward the end of a scholarly career as a humanities writer as well as public service as a diplomat in Asia, returned to the United States and used the family money to build himself a nice observatory in Flagstaff Arizona. The Lowell Observatory’s remote location was the first such site selected specifically for the advantages of it’s favourable altitude (about 7,000 feet), and its distance from the blinding effects of urban light pollution.
There Percival spent the next ten years or so studying Mars and Venus. He fired a lot of imaginations at the time — and set forth an entire genre of science fiction — by way of three books he wrote describing a network of canals he could make out through his 61 cm (24 inch) telescope, which crisscrossed the planet’s surface, and which he interpreted to be signs of an intelligent civilization with water supply problems on a dry planet. These were later determined to be natural geological features. He also described spoke like lines on Venus, with a dark dot at the centre, which has since been speculated to have been the reflection of his own eyeball looking out into the daylight sky at Venus, using a heavily stopped down lens aperture that provided the mirror like effect.
The last decade of his career and his life Percival spent looking for ‘Planet X’, that still undiscovered celestial body evidenced by its perturbing influences on the outermost planets of the solar system. Percival was, like many other astronomers at the time, very keen to be first to discover this mystery planet.
Percy passed away unfulfilled in his quest, however, and in 1929 (after a lengthy dispute between his widow and the observatory regarding the benefit of his financial legacy), young Clyde Tombaugh was hired to pick up the torch and continue Percival’s search for Planet X, in the very same part of the sky where the old man had left off. After about a year, while using a device called a ‘blink separator’ (which basically displays side-by-side, consecutive pictures of the sky to make it apparent if anything moved), Clyde stumbled upon his discovery of Pluto.
This was a very big deal, for Clyde and the world as a whole, and once the presence of Pluto was confirmed, the astronomical community uttered a collective ‘eureka’ — as scientific types are wont to do — and became satisfied that the ‘Planet X’ mystery had been resolved at last. Pluto was the gravitational culprit they’d been seeking all this time.
However, once again things did not end there. Pluto’s stature as the 9th planet faded steadily over the next four decades. Clyde’s big find was originally estimated to be about the size of Earth. Then in 1948, further estimations revised Pluto’s size down to roughly one-tenth of the Earth’s mass. In 1976 they looked again and decided, okay, let’s make that around 1 per cent of the size of Earth. Two years after that they discovered Charon, one of Pluto’s five moons, which weighed in at about half of Pluto’s size. The proximity of Charon permitted the most accurate calculations yet to reveal Pluto as just a measly 1/500th the mass of Earth — or only about 1/6th the mass of our own moon. This little thing could not possibly be what had been jerking around Uranus and Neptune after all. So what, then, was doing it?
Suddenly the search for Planet X was back on for a time, then abruptly called off when, as usual, facts ruined everything: A 1992 analysis of data from the space probe Voyager 2’s 1989 flyby of Neptune resulted in that planet’s mass being re-estimated downward by about a half percent, and then when when all the numbers where run again, everything now checked out fine. Turns out there was no need for a missing piece to any Neptune / Uranus puzzle after all.
Meanwhile, Pluto’s slide continued down the Kuiper Belt, tumbling from its rise to textbook and B-movie fame steadily back down to the final insult: Loss of its planetary status in 2006, the year when an even larger rock was discovered in an orbit very similar to Pluto’s. Perhaps, scientists began to realize, there could be dozens, or even hundreds more of those things just waiting to be found as exploration continued. And so, faced with the prospect of having to grant so many more such objects coveted status as planets, the International Astronomical Union made a tough love decision to formally define what it means to be a planet, to the exclusion of poor little Pluto. The IAU demoted Pluto and other Pluto-sized objects to a sub-classification called ‘dwarf planets’, and thus spared the solar system from going condo.
Pluto’s rise and fall from planetary grace was staggeringly fast in light of the fact that, in the 46 years that Pluto featured in school textbooks as as the 9th planet, it had only managed to complete less than one fifth of its 247-year-or-so orbit around the sun. But in that time it had taken its place as a part of the planetary solar system for a whole generation. And despite a new, vaguely felon-like designation of Minor Planet 134340 Pluto, fans around the world to this day still refuse to relinquish their affection for little Pluto as planet Number 9 in their hearts, if not science class curriculum.
Which brings us to a particularly interesting part of the story. In January 2006, about 7 months before Pluto ran afoul of the revised planetary definitions, NASA launched a spacecraft called New Horizons which, in July, 2015, will be completing a nine-and-a-half year journey to go see Pluto and it’s little buddy Charon. New Horizons is equipped with all kinds of radio and spectroscopic gadgets it will deploy in a six month study during the approach to Pluto and Charon and as it zooms by. The probe will also of course be sending home some nice travel snap close ups of the two for keepsakes, and will then continue on to see what else is up in the Kuiper Belt.
Now let’s stop for a moment and think about how very cool that is: A one thousand-pound, piano-sized, robotic probe is out there, zooming far away from us through space, at about 84,000 km/hr (52,000 miles/hr) even as you read this. In fact by December, 2013, the New Horizons was already so far away that its radio signals were taking about 4 hours to reach Earth; or around 8 hours round trip. That is ‘holy crap’ far, when one considers that radio signals to Earth from the Sun take about eight minutes to get here. In fact, back in December, 2012, New Horizons had crossed the halfway point, and has ever since been hurtling through space closer and closer to Pluto than to Earth.
That little machine’s flight is also marked by the distinction of reaching the fastest propelled speed ever achieved by a human-made object, heaved into space toward a little chunk of ice and rock out at the farthest, darkest, coldest edge of our solar system.
But here is the coolest part: New Horizons is also carrying a very special payload. On board for the roughly 5 billion kilometre (about 3 billion mile) trip are Clyde Tombough’s ashes, who died in 1997, and who would no doubt be very pleased with how all of this panned out. Talk about having your ashes scattered.
So this, then, has been the story of how for centuries astronomy’s misdirected search for a planet that didn’t exist led to a young man’s achievement of worldwide fame, and a place in history, for stumbling across another planet altogether — which then turned out not even to be a planet after all.
But in its brief, glorious time of mistaken identity, the little chunk of rock and ice he spotted generated sufficient interest and wonder for hundreds of scientists and engineers to get together and build a technological marvel to go check it out. And when they launched it, they packed inside the cremated remains of our young Clyde, last in line to a misguided search across centuries, traveling across the solar system for an appointment with his most famous mistake at a few minutes before noon, UTC, on July 14, 2015.
This is a story comprised of a long chain of errors and disappointments. Yet it is ultimately uplifting by way of outcome, and thus it is a story that illustrates how the void where cold facts drop away — where people make mistakes — can become a warm place where poetry rises to fill the void.