Outrage: Pluto, Already Demoted from Planet to "Dwarf Planet," Now Stripped of Even that Dignity and Called a "Plutoid"

Har.

Disgruntled scientists renewed their vows this week to call Pluto a planet despite an international governing body's latest ruling to reclassify the tiny world.

On Wednesday, the International Astronomical Union (IAU) declared that Pluto will henceforth be known as a "plutoid," a new class of objects that has two members (the other being Eris, a small body beyond Pluto). The IAU, considered in charge of naming celestial objects, has been around since 1919. It demoted Pluto to "dwarf planet" status in 2006.

The latest decision was announced by email to the press, and it took researchers by surprise. Even IAU members and astronomers who discovered Eris and other objects that might eventually be called plutoids were not consulted or informed.

That's left many scientists peeved that the IAU developed the new term and its definition behind closed doors. They accuse the IAU of being secretive, out of touch and of failing to consider basic physical characteristics that researchers use to define planets.

"The derision for this group [the IAU] is now spreading virally," said Alan Stern, former assistant administrator for the Science Mission Directorate at NASA and lead investigator for the New Horizons mission to Pluto.

Stern has also hinted that a rival group to the IAU might be formed. When asked about this possibility, he said: "There is a disturbance in the force. Enough said."

This IAU seems to be going out of its way to just make up new definitions. The argument that Pluto is not a planet can be put simply: It's not really all that big, and there are other objects of about its size, so calling Pluto a planet invites the question, why not call Eris a planet too?

It's a decent argument, I guess, though I don't know why Eris can't be a planet too. And check out how convoluted this is:

The new IAU definition of plutoid: "Plutoids are celestial bodies in orbit around the sun at a distance greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighborhood around their orbit."

Sykes and some other astronomers prefer to consider planets based on "shared physical characteristics." He says the geophysical definition for a planet is this: "A planet is a round object (in hydrostatic equilibrium) that orbits a star." He notes that objects large enough to make themselves round tend to have signs of geology (volcanism, tectonics and atmospheres) that don't exist on smaller objects.

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"It's hard to find anyone who thinks this is (i) necessary, (ii) a step forward, or even (iii) useful," Stern said in an email interview. And of the new plutoid ruling: "About all it has accomplished is to convert some people who were on the fence to agreeing with those of us that planet definition needs a rethink" and that the process needs to be "out in the open."

Honestly, at this point, they just seem to be issuing these pointless redefinitions because it's the only way the great mass of the public even hears of the scary-authority of the IAU.

posted by Ace at 08:46 PM

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