The model you made of Earth's solar system in elementary school is obsolete. If it includes Pluto, anyway.
Thanks to a controversial August 2006 demotion, Pluto was rendered a dwarf planet. And Neil deGrasse Tyson helped lead the charge by refusing to refer to Pluto as the solar system's ninth planet in the Hayden Planetarium's display. Pluto, with its elongated orbit and 50 percent ice composition, was too different from the other planets, Tyson insisted; it was simply the first of a new class of objects that weren't realized until the early 1990s [source: NPR].
Pluto and Tyson, who were dubbed "frenemies," began a complicated relationship that played out in the media. While Tyson's been quick to say he wasn't solely responsible for Pluto's "killing off" as a planet, he admits he was an accessory to the fact. "All I did was drive the getaway car" [source: Houston].
Professionally, Tyson stands by his actions. Personally, however, his feelings remain mixed. So much so that three years after Pluto's demotion, he opened up on his blog. "I feel compelled to defend Pluto's honor," Tyson wrote. "It lives deeply in our 20th century culture and consciousness and somehow rounds out the diversity of our family of planets like the troubled sibling of a large family."