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If you were looking forward to seeing astrophysicist and "Cosmos" host Neil deGrasse Tyson debate how Pluto should be classified, don't hold your breath. Tyson says he's done debating.

The planetary scientist in charge of NASA's New Horizons mission to Pluto and the Kuiper Belt, Alan Stern, issued the debate challenge in an NBC News interview a week ago. As director of New York's Hayden Planetarium, Tyson left Pluto out of the facility's main planetary lineup, and wrote a book about the controversy called "The Pluto Files."

(Full disclosure: I also wrote a book on the subject, titled "The Case for Pluto.")

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The International Astronomical Union considers Pluto to be a dwarf planet, and not a full-fledged planet, because it has not "cleared the neighborhood around its orbit." Stern told NBC News last week that Pluto deserved full planetary status, and he wanted to debate the issue with Tyson. "I am challenging him to the equivalent of the 'Thrilla in Manila,'" Stern said.

When a Facebook fan asked Tyson about the challenge, he said he'd pass on the invitation.

Astrophysicist Neil deGrasse Tyson shook up the planetary lineup as director of New York's Hayden Planetarium.David Britt-Friedman / NBC News file

"As a general rule, I don't debate people," Tyson wrote. "Done it once or twice before, but abandoned the effort. What's behind it is that I don't have opinions that I require other people to have. So debates don't interest me for this reason."

Tyson did participate in a "Great Planet Debate" back in 2008, but Stern didn't take part in that event.

On his own Facebook page, Stern criticized Tyson's no-debate policy. "All scientists engage in debate over competing ideas," Stern wrote. "If he persists in not supporting his position by engaging in debate, I'll consider it evidence he knows the position isn't supportable."

Tip o' the Log to's Mark Whittington