Look, Pluto had a good run. While 76 years is nothing in astronomical time, in the human span it's a whole lifetime. For all those decades, Pluto was regarded as a planet, the smallest and most distant member of our solar system family. It had an affectionate place in human hearts, and a Disney cartoon character and an element as famous namesakes. And then, Mike Brown killed it.
He admits as much; it's the title of his book, "How I Killed Pluto and Why It Had It Coming." In 2005, the Caltech astronomer found, in the same neighborhood as Pluto, an object at least as big as Pluto, which he called Eris. It not only looked like another planet, it looked like there could be more like it out there. The world of astronomy had to decide: Either all of these newcomers would have to be defined as planets too, which kind of lowered the tone of the whole solar system, or the definition of "planet" would have to get more exclusive, which meant that Pluto would be booted from the planet club. That happened in 2006. Who knew a scientific definition could get everyone so emotional?
How could you not, well, go into space, growing up where you did?
I grew up in Huntsville, Ala., where they were building the rockets. As a kid you'd be playing and suddenly you'd hear brrrrrr, feel the ground shake, and it was the Saturn 5s being tested. We had an astronaut down the street. My father worked on the Apollo landers and moon rovers. So it seemed everybody wanted to do something with space.
But not necessarily with the solar system, right?
When I was in grad school, the solar system was really the runt of astronomy. People who did work in the solar system were deemed slightly pathetic. Everybody would pat you on the head and say, "That's nice -- you look at planets? I can look at planets without even using a telescope."
So there's this pecking order in astronomy. If you studied the most distant things, you were the coolest person around. The discovery in 1992 of the Kuiper Belt [a massive cluster of space objects beyond Neptune] that made it suddenly obvious that we didn't know [everything] about the solar system.
It's right there over everybody's head and nobody looks. That is the part that amazes me. You don't notice because you forget to look.
And you started looking there.
I was convinced there was another planet out there past Pluto. The only way to find it was to look at the whole sky, and modern telescopes look at about this much [he puts his fingers close together]. The Palomar Observatory telescope had stopped being used a long time ago because people had already looked at the whole sky -- why bother looking again? So I started using Palomar's 48-inch Samuel Oschin Telescope. You have to look for things in the solar system that move. The only way is to take two pictures and look for something that's [changed position]. The very first picture of Eris was taken by the exact same telescope in 1954.
In his book, "A Short History of Nearly Everything," Bill Bryson writes that our sense of the solar system as a kind of cozy place is out of whack; if Earth were the size of a pea, Pluto would be a bacterium a mile and a half away -- hardly neighborly.
One of the reasons the public is still so in love with Pluto is this incredibly incorrect sense of Pluto's place in the solar system. My own daughter has a placemat that has nine planets, and Pluto is the smallest, but just barely -- who wouldn't think that [it] deserved to be a planet? But it's such an incorrect view of what the actual solar system is like. When I show people a picture of [the planets'] actual sizes, they gasp. I understand why people feel that way about Pluto, but they're feeling that way about the fictional Pluto. In light hours, Pluto is about 4 hours out [from the sun]. We are 8 minutes.
What was your eureka moment?
I was sitting in this very chair looking at pictures on the computer that the robotic telescope had taken the night before. The software would pick out potential things that were moving [by comparing photo images] -- most[ly] it would be cat hairs or an airplane, things that computers are not very good at distinguishing. That morning, I was clicking through and I got to this one. The fact that it was the brightest thing I'd ever seen, and most distant, meant this thing had to be huge. So I went back and double checked, and I realized, oh my God, this is actually real. This thing is bigger than Pluto. I picked up the phone and called my wife and said, 'I just found a planet.'
Did you foresee the repercussions, astronomical and social?
