Size matters

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Poor Pluto is going through an identity crisis.

Some scientists believe it’s not really a planet, but some forlorn rock that belongs in the Kuiper Belt – the remains of the outer disk that originally formed our solar system.

Is this planetary discrimination? Or are we trying to force an object to fit into a system where it clearly doesn’t belong?

One problem is that scientists haven’t defined what a planet is. One general explanation is – an object whose luminosity is fainter than that of the star it orbits. Since Pluto orbits a star (the Sun, for those of you out there orbiting your own galaxy), and is also much less luminous, then it satisfies the criteria and stands a decent chance of retaining its status of 9th Planet.

But wait…. there’s also a matter of size.

Pluto is so small (2,200 kilometer diameter) it might not be worthy of full planet status. It’s less than half the size of any other planet in our system …. in fact it’s even smaller than our moon.

And it marches to the beat of its own drum, with an orbit at an angle from the plane of the other planets traveling around the Sun.

The 9th planet was discovered 75 years ago by an American, before the discovery of the Kuiper Belt. Astronomers now argue that had they known of the existence of the belt, Pluto would have been classified as a giant Kuiper Belt Object (KBO) – like Ceres in the Asteroid Belt.

Some believe the reason the debate hasn’t settled is because Pluto’s discovery in 1930 was made by U.S. astronomer Clyde Tombaugh – and it’s the only “planet” discovered by Americans.

Until this week.

A team of researchers from CalTech, Yale, and the Gemini Observatory in Hilo, HI, report the discovery of a new outer “planet” – 2003 UB313, a giant lump of rock and ice, and the largest object detected in the solar system since the discovery of Neptune and its moon Triton in 1846.

So once again astronomers can’t agree whether 2003 UB313 is a planet or just a suped-up asteroid. Its discoverers claim it is the 10th planet, but other astronomers, the ones who want to downgrade Pluto to a minor planet, insist it’s just another KBO.

Clearly, there are more important matters going on in the world.

I mean, who really cares whether Pluto and 2003 UB313 are classified as planets or KBOs or asteroids?

Our President on Monday endorsed teaching intelligent design as an alternative to evolution in our classrooms. This week, 21 Marines and an interpreter were killed in Iraq. And U.S. intelligence predicts Iran is about ten years away from manufacturing the key ingredient for a nuclear bomb – in other words they’ll probably have a weapon up and running in a couple years.

So why am I taking space to write about some obscure astronomical debate? Because it could turn vicious. Pluto’s fate is in the balance as well as millions of science textbooks and plastic placemats. And maybe, just maybe, a reasonable solution will appear that might inform other world crises.

There could be a compromise. Pluto could remain a planet, as well as a KBO. And all other KBOs would be categorized as KBOs, with no nonsense to recognize them as major planets.

So what do you think?


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