The Great (and Sometimes Serious) Debate About Pluto Jeanna Bryner
Senior Writer
SPACE.com
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.

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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
head."


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