Mike Brown collects rock spheres to represent the planetoids he's found beyond Pluto.

Mike Brown grew up near NASA's Marshall Space Flight Center in Huntsville, Alabama, where his dad and every other dad in the neighborhood worked on Saturn rockets. Occasionally, the earth would rumble as he studied at his desk in a room dominated by a poster of the solar system. The shaking signaled yet another rocket test.

Decades later, Brown and his colleagues, Chad Trujillo of Gemini Observatory and David Rabinowitz of Yale University, have shaken the world of astronomy right down to that solar system poster, finding orbital objects as far as 10 billion miles from the sun in a ring of debris called the Kuiper belt. They nicknamed those icy bodies Quaoar, Sedna, Santa, Easter Bunny, and Xena.

The most important find is Sedna, which Brown calls a fossil that could lead to the unraveling of the history of the solar system. But the one that has caused the biggest uproar among astronomers is Xena, recently confirmed by a team of German scientists as being at least 30 percent larger than Pluto.

Xena prompted an ongoing debate in the International Astronomical Union as to whether it should be formally recognized as the 10th planet, or whether Pluto should be demoted and the number of planets reduced to eight. Whatever the decision, ultimately every elementary school science textbook will need to be rewritten and every solar system poster revised.

If you knew me as a first- or ­second-year graduate student in astronomy at the University of California at Berkeley, you're probably a little surprised to be reading about me now.

I didn't quite fit back then. I lived in a sailboat in the Berkeley marina and spent most of my time backpacking. Then came a big transformational moment. And the only reason I remember it being transformational is because afterward it happened again.

I went to the University of California's Lick Observatory with my academic adviser, and we were using this monstrous three-meter (120 inch) telescope. It was like a cathedral, actually, and a guy at the observatory mentioned this little telescope attached to the side of the big one. He said nobody used it because it was small and you couldn't really see much with it. I can still remember the feeling twisting in my stomach: That's wrong.

It's so hard to get time on a telescope. It's just wrong to have telescopes that don't get used. So I walked around for six months thinking there must be some way to take advantage of them all the time. It's completely backward from how anybody else figures out a Ph.D. project. Nobody finds a telescope and then, having no research topic in mind, spends a long time wondering what to do with it.

That telescope led me to study Io, one of the moons of Jupiter, focusing on its volcanoes and on how it interacts with Jupiter's magnetic field. For my Ph.D. thesis I used the telescope to observe Io for six months straight, watching volcanoes going off and then watching the changes.

Brown and his team collect data daily via a microwave link to Mount Palomar's Samuel Oschin Telescope (Above and below)

But you know what that telescope really did? It made me very alert when the next transformational moment came along.

I was walking down the hall past the office next to mine—the office of a postdoc named Jane Luu—when I heard this urgent whisper: "C'mere!" Jane led me to her computer screen and showed me what she and Dave Jewitt had just discovered far beyond Pluto: the first Kuiper belt object.

This was 1992. It's funny now to think back on it. The day before, the Kuiper belt was thought of as a repository of comets that were maybe a kilometer across. This object was a couple of hundred kilometers across. The day before that discovery, the idea that there were large objects out there simply hadn't occurred to most people. And when it came time for me to think about what to do next, this was obviously the place to look.

My work on Io led me to Caltech, which is a fantastic place for an astronomer. But it was pretty different from what I was used to—that small telescope and a lot of access. At Caltech, you have access to really big telescopes—some of the greatest in the world—but for only a few nights a year. It makes a big difference in how you do astronomy, and to be honest, I felt uneasy. I liked the style that I'd used on Io and actually told my father I was thinking about leaving. He promptly responded that if I left Caltech I was a nut.

Just a few months later, I was using the big 200-inch Hale Telescope at Caltech's Palomar Observatory. It was a snowy night, and we couldn't view anything, so I headed off to the place where you can sleep. On the way, I ran into a staff member who wanted to show me the Samuel Oschin Telescope, a 48-inch instrument that had been used for 50 years to do the Palomar Observatory Sky Survey.

Astronomers all know the Palomar sky survey. It was huge. It took photographic plates everywhere across the sky, and these plates were reproduced on film and sent to every astronomy library in the world, which allowed anybody to get out a jewelers' loupe and look at whatever part of the sky he or she wished.

They were just about done with the second-generation survey, and this staff member told me that, basically, when the telescope finished there would be nothing else for it to do, and it was just going to sit there. I thought, "Oh, no, it's not!"