Tucson scientist argues vs. Pluto’s demotion
by Alan Fischer on Aug. 14, 2008, under Local, Nation/World, SpecialMark Sykes wants additions for total of 13 planets
Sykes
A Tucson planetary scientist argues that Pluto and four other small space bodies should be added to our solar system’s list of planets to bring the total to 13.
Mark Sykes, director of the Tucson-based Planetary Science Institute, disagrees with the definition of a planet that the International Astronomical Union voted into place in 2006, which demoted Pluto from the ranks of planets.
“My problem with it is not so much the status of Pluto,” he said of the union’s planet definition. “It’s not useful to do the kinds of science we do in solar system exploration. It has no usefulness for people interested in understanding where geology occurs.
“It’s a bad message to send to the public,” Sykes said Wednesday. “When you have a decision based on a vote it is politics; it is not science.”
“Pluto haters” squared off against “Pluto huggers” for the vote, he said.
“Pluto haters worked the political system to have a vote on a definition that would exclude Pluto,” he said.
“The IAU definition serves a very narrow segment of the astronomical community. It’s not very useful for the rest of us,” Sykes said.
He believes a planet should be defined as an object massive enough to be round that orbits around a star.
Sykes will debate Thursday with Neil deGrasse Tyson, host of PBS’ NOVA scienceNOW television program, on planetary definitions and the place of Pluto and other objects in the solar system.
The debate will take place at a three-day “Great Planet Debate: Science as a Process” conference that ends Saturday at the Johns Hopkins Applied Physics Laboratory near Columbia, Md.
The union definition approved in 2006 states that a planet is a body that orbits the sun, is large enough for its own gravity to make it round, and has cleared its orbit of smaller objects.
“Pluto was not big enough at its distance from the sun to have cleared its orbit, so it was excluded,” Sykes said.
The union definition uses advanced dynamical calculations that show an object’s impact on the movement of other objects, he said, rather than the properties of the body itself.
Tiny Pluto, far from the sun, does not affect the motion of other objects so it was axed from the list of planets, he said. Pluto is about two-thirds the size of the moon.
Under the latest definition, a body must be more and more massive the farther it is from the sun to be deemed a planet, he said.
“If you swapped Jupiter and the Earth, the Earth is no longer a planet,” he said “It’s like saying a fruit becomes a vegetable if you move it to the other side of the table. What sense does that make? Why would the Earth’s planethood depend on where it is located?”
The union recognizes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Sykes believes that five bodies classified as “dwarf planets” – Pluto, Ceres, Charon, Eris and Makemake – should be termed planets.
Additional new discoveries could be added to the list, he said.
The demotion of Pluto from planet status has sparked public interest and passion, which he hopes the debate will fuel.
But the event will result in a public exchange of ideas rather than one side declaring victory.
“People can see why this perspective is useful, why that perspective is useful, and which is more useful in something like teaching kids,” Sykes said.
“It’s a real opportunity to use that passion to explain why people think different ways and the value of that, and what science is really about.”
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Planetary Science Institute Web site: www.psi.edu/
