Cal Tech astronomer Mike Brown is the man reponsible for demoting Pluto.
Cal Tech astronomer Mike Brown has been driven by a single goal: to find other planets in our universe. While he didn't officially discover another planet, his Ahab-like obsession led to a revolutionary reconsideration of exactly how we define a "planet." Brown actually discovered the largest object found in our solar system in the past 150 years. He called it Eris, and it was 27 percent larger than Pluto. If Pluto was a planet, then surely Eris was, too.
Rather than lobby the astronomy community to declare Eris a 10th planet, Brown did something so selfless that it's breathtaking. As a scientific consensus was developing around declaring Brown's discovery a planet, which would have instantly put Brown in the pantheon of great scientists, he instead became the strongest advocate against declaring his find a planet. Instead, he called for a redefinition of "planet" that would exclude both Eris and Pluto: "Singling [Pluto] out for planetary status really made no sense at all." Brown would win his case.
Brown's brilliant scientific memoir brings clarity and elegance to the complexities of planetary science. Brown is also a surprisingly self-effacing and entertaining genius. But what comes through clearest is his uncompromising integrity, his "take-no-prisoners" belief in science. He puts principle above his own best interest. "Whether or not Pluto is a planet is critical to our understanding of the solar system," he writes, near the end of his out-of-this-world science memoir.