How I Killed Pluto and Why It Had It Coming - Mike Brown [55]
Clyde Tombaugh found Pluto in 1930 but spent much of the following decades searching for whatever else might be out there in the distant regions beyond Neptune. He never found anything else. As the story is usually told, this was because he was using the old technology of photographic plates, which were simply not good enough to see what we now know as the myriads of objects out there. But we now know that the story is not quite so simple. If Tombaugh had been looking 278 years earlier or 278 years later, our new object would have been as bright as Pluto, and he would have found both.
It’s interesting to ponder what people would have thought in the 1930s if not just Pluto but also this new object had been found. Both are on crazy elongated orbits. Both appear significantly smaller than the giant planets. And their orbits cross. I’m pretty sure that the similarities to the asteroid belt discoveries 130 years earlier would have led everyone to conclude that these were simply the biggest members of what would turn out to be a huge population of similar objects. And they would have been right. Instead, though, the solar system was arranged such that at the time of the development of large photographic plates and the first major survey of the outer solar system, only Pluto was close enough to be seen. Too bad for us not to have been provided with such obvious clues to the nature of the outer solar system. But good for Pluto, since it got to be everybody’s favorite oddball planet for more than seventy-five years. Though it wouldn’t be for much longer.
We didn’t refer to our discovery as “this new object” for long. We quickly gave it a code name. Unlike Flying Dutchman or Santa, which were inspired by circumstances of the discovery, we had had a name waiting for this one for a long time. Since the earliest days of surveying the outer solar system with the photographic plates, I had always had a well-considered code name for the hypothetical object bigger than Pluto. In coming up with the name, I had thought that it was best to keep the X for the apocryphal Planet X beyond Neptune. And I had thought that Venus shouldn’t remain the only female among the planets. And finally, I thought that the name should be mythological.
With those criteria, I was left, as far as I could tell, with only one choice. We called the new object Xena, after the eponymous heroine of Xena: Warrior Princess, the campy, female-empowered television take on Greek mythology starring Lucy Lawless. It was true that the name Xena was only TV mythology instead of real mythology, but as I liked to point out for the next eighteen months, as the name got more and more widely known, wasn’t Pluto named after a Disney dog? Whenever I made that joke publicly, about half the people in the room actually thought I was serious.
A few weeks after the discovery of Xena, Chad got a chance to swing the giant Gemini telescope, at the summit of Mauna Kea on the Big Island of Hawaii, in its direction. Chad now worked at that telescope, so getting a little time at the discretion of the director to look at something that was clearly bigger than Pluto was no hard task. When he looked at Xena’s surface, we had our first confirmation that Xena was something special. Xena looked like Pluto.
By “looked like Pluto” what I really mean, to be more precise, is that the sunlight bouncing off Xena contained within it the unmistakable signature of a surface covered in solid frozen methane. Nothing else in the Kuiper belt looked like this, with one exception: Pluto.
It was one thing