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602The Great (and Sometimes Serious) Debate About Pluto

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  • Robert Blake
    Aug 15, 2008
      The Great (and Sometimes Serious) Debate About Pluto Jeanna Bryner
      Senior Writer
      2 hours, 25 minutes ago

      LAUREL, MD — The entrance to the debate over Pluto's planet status
      said it all: With techno music blaring in the background, the two
      debaters and a moderator walked into the auditorium, cameras flashing
      and the audience clapping.


      One debater, Neil deGrasse Tyson, did the boxing entrance à la Rocky.
      That's how hot the matchup is between Pluto as a planet and Pluto as
      a plutoid.

      Tyson, director of the American Museum of Natural History's Hayden
      Planetarium in New York, supports the demotion of Pluto. In the other
      corner, Mark Sykes, director of the Planetary Science Institute in
      Tuscon, Ariz., does not agree with the recent ruling that essentially
      booted Pluto from the planet lineup.

      The debate over whether Pluto should be considered a planet is part
      of "The Great Planet Debate: Science as Process" conference here at
      the Johns Hopkins University Applied Physics Laboratory (APL) that
      runs through Saturday.

      Before the idea-throwing began, debate moderator Ira Flatow of
      National Public Radio's Science Friday threw out his own rule, "No
      throwing of perishable items or missiles of any kind at the stage,"
      Flatow said with a smirk.

      In fact, the debate was filled with lots of applause, laughter and
      some snide remarks, but mostly it was a friendly tussle. In fact,
      neither Tyson nor Sykes clearly defined their specific positions on
      Pluto and the definition of a planet.

      How many planets?

      In general, Tyson said astronomers need to come up with an entirely
      new lexicon to group planets and planet-like objects together. He
      also said Pluto is not like the other eight major planets in the
      solar system and that it instead fits into the Kuiper Belt, a vast
      region of objects beyond the orbit of Neptune.

      "And I am certain Pluto is happier there," Tyson said.

      Sykes said that if a non-stellar object is massive enough to be round
      and it orbits a star, it ought to be a planet. Under this definition,
      the solar system would have 13 planets, although more might be found
      in the future beyond the orbit of Pluto. In addition to Pluto and the
      other eight major planets, these would also include Ceres, Pluto's
      moon Charon, Eris, and recently discovered Makemake.

      In response to Sykes wanting to call all of these objects "planets,"
      Tyson responded, "You need that word. I'm saying define it however
      you want and then recognize how useless it is and then find another
      term to group objects of like properties that are useful to planetary
      scientists," Tyson said.

      Tyson would rather not count planets and instead group objects
      together that have similar properties, even if that means having
      handfuls and handfuls of planets.

      Pluto tale

      The debate marks another chapter in the Pluto saga, which began when
      Pluto was discovered in 1930, as this object was an oddball compared
      with its solar system buddies in its eccentric orbit, small size and
      low mass (it is less massive than Earth's moon).

      Some argued, then, that Pluto didn't fit in with the rest of the
      solar system planets. The plot thickened in 2004 with the discovery
      of Sedna, an object about three-fourths Pluto's size and about three
      times as far from the sun. If Pluto fits the planet build then so
      would Sedna.

      Caltech's Mike Brown added another twist to the story in 2005 when he
      announced the discovery of 2003 UB313, a hopeful 10th planet in our
      solar system. The object was round, orbited the sun, and the kicker —
      it turned out to be larger than our then ninth planet, Pluto. In
      2006, UB313 was officially named Eris.

      "The Pluto controversy boiled up when Eris came up, because you
      couldn't leave things the way they were," said Jack Lissauer of NASA
      Ames Research Center in California. "You really had to contort things
      to say Pluto was a planet and Eris wasn't. Things really came to a

      Since then, the International Astronomical Union (IAU) has labeled
      Pluto a "dwarf planet" and then later, a "plutoid." Many planet
      scientists were disgruntled over the 2006 IAU decision, which they
      said involved a vote of just 424 astronomers out of some 10,000
      professional astronomers and many other planetary scientists around
      the globe.

      "Having a group of graybeards getting together and issuing a formal
      definition is not a good idea," David Morrison of NASA Ames, told
      SPACE.com, referring to the IAU's 2006 vote.

      Delusion or debate?

      Hal Weaver of JHU's Applied Physics Laboratory, called this week's
      debate "a real scientific conference to lay out all the issues and
      discuss them."

      But Lissauer pointed out that even this conference has its
      flaws. "This meeting isn't representative of planetary scientists
      either. There is a very, very skewed distribution," Lissauer said
      during a panel discussion.

      No consensus was reached Thursday.

      At the end of the debate, Pluto, as far as many astronomers are
      concerned, remains in some sort of limbo.

      And closing the debate, Sykes said, "I get the feeling Neil [Tyson]
      is coming over to the right side of the fence."

      Tyson's response: "The delusion continues."

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      Original Story: The Great (and Sometimes Serious) Debate About Pluto