Pluto_planet.jpg

(ultra.wikia.com)

The Harvard-Smithsonian Center for Astrophysics held a debate a couple of weeks ago on the varying definitions about what does and does not qualify as a planet.

The vote at the end of the debate has reignited discussion over the definitions and may have opened to door to Pluto's victorious return to its status as a planet in our solar system.

This is a bummer since we've just reprinted all of the text books to exclude Pluto and the fake internet rage has just begun to subside.

You see, the International Astronomical Union (IAU) has three conditions for a celestial body to be recognized as a planet.

According to the IAU website, a celestial body qualifies as a planet if and only if it:

is in orbit around the Sun has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighbourhood around its orbit.

It's this third condition that causes the confusion, and not because of the bizarre, British spelling of neighborhood.

What it means for a celestial body to "clear its neighborhood" is that it is distinctly larger in size than other items around it.

Back in 2005, a scientist named Mike Brown discovered a celestial body that was slightly larger than Pluto. He named it Xena (after your favorite warrior princess) and called it the 10th planet.

This cause a lot of worry in the scientific community because of the possible slippery slope. If we were to arbitrarily add orbiting rocks to our solar system, we may suddenly have to add lots of new items that would have never before been considered planets.

Can you imagine the catastrophe? Shoe boxes would no longer be large enough for elementary school models, canonical mnemonic devices would have to be revised and extended, oh the humanity!

Instead, the IAU decided to simplify things and downgraded Pluto to "dwarf planet" status: A move that has landed in the halls of internet infamy.

The debate was last week at Harvard. From the CfA website:

"Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU's viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the exoplanet scientist's viewpoint.

Gingerich argued that 'a planet is a culturally defined word that changes over time,' and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as 'the smallest spherical lump of matter that formed around stars or stellar remnants,' which means Pluto is a planet."

After the debate was through, the audience voted on Pluto's fate and decided that it, along with several other celestial bodies, ought to be admitted back into the grandeur that is planetary status.

Of course, this doesn't do much to modify the definition and classifications of the IAU, but it has inflamed the discussion once again and highlighted some of the resistance we saw back in 2006 when this resolution was passed. Is it time for another discussion on the matter?

I'd like to take a moment to say that this discussion is not a point against the scientific enterprise. Rather, this search for distinct and specific definitions is part of the exercise of good science.

We'll sort all of this out eventually. It may just mean the reprinting of textbooks. Again.

In other news: Pluto is a dark, frozen rock in the outer recesses of our solar system and does not care in the least how we classify it.

#bhamtech

P.S. You can watch the full debate here: