By now it seemed to me inevitable that, whether anyone realized it or not, astronomers were on an unstoppable march that would eventually lead to a tenth planet. It seemed to me obvious that it was there, slowly circling the sun, just waiting for the moment when someone somewhere pointed a telescope at the right spot, noticed something that hadn’t been there earlier, and suddenly announced to an unsuspecting world that our solar system had more than nine planets.
Sitting beneath the massive Hale Telescope that foggy night, ever the scientist, Sabine asked, “What evidence do you have?”
I told her about all of the recent astronomical discoveries. But when pressed for evidence, I had to admit: I had none whatsoever. I had a hunch. Officially, scientists don’t work on hunches. We work on hypotheses and observations and plenty of evidence. Hunches don’t get you research funding, tenure at your university, or access to the world’s largest telescopes. But a hunch was all I had. No one had systematically looked across the sky for a new planet since the 1930s, when Pluto itself was found, and even though astronomers knew of almost five hundred bodies in the Kuiper belt, the searches had been, of necessity, piecemeal, and no one had yet mounted a careful search like the one that had uncovered Pluto. Now, seventy years after the discovery of Pluto, telescopes were bigger and better, computers made searches vastly more powerful, and astronomers simply knew more about what they were looking for. How could it be that if someone went and looked again for a new planet they wouldn’t find something that had been just beyond the reach of the telescopes in the 1930s? There had to be a tenth planet. The possibility that Pluto was a unique planetary oddball out at the edge of the solar system seemed absurd to me.
~Mike Brown, How I Killed Pluto and Why It Had It Coming