Wed, Aug

And Then There Were Twelve...

Wed, Aug 16, 2006


(Graphic from the Globe and Mail)

Take a moment and mark this date down, as the day that our universe changed. It’s not every day that we add a new planet to our solar system. In fact, we haven’t done that since 1930. And never have we added three planets at once.

The International Astronomical Union has, after months of controversy and debate, issued a draft resolution officially reaffirming Pluto has a planet, and then adding three other objects to our list of planets: Pluto’s former moon, Charon, as well as Ceres in the asteroid belt and the Kuiper Belt object 2003 UB313, unofficially nicknamed Xena.

According to the new draft definition, two conditions must be satisfied for an object to be called a “planet.” First, the object must be in orbit around a star, while not being itself a star. Second, the object must be large enough (or more technically correct, massive enough) for its own gravity to pull it into a nearly spherical shape. The shape of objects with mass above 5 x 1020 kg and diameter greater than 800 km would normally be determined by self-gravity, but all borderline cases would have to be established by observation.

But like many committee decisions, this statement is causing its own controversies. I heard a scientist on Nova Science Now say that if we moved Pluto into Earth’s orbit around the sun, Pluto would grow a tail, and we already have a name for objects that grow tails in this situation: comets. Pluto is looking more and more like a Kuiper Belt object, and under the new rules, another forty objects could end up joining our list of planets.

I myself have a problem with the designation of Charon as a separate planet, unless astronomers want to pair it up with Pluto as a “twin planet” and refer to the pair as a single celestial object. You know, Pluto and Charon, like Newfoundland and Labrador.

I joke, but I think a fair argument can be made that these new rules are an attempt to avoid taking the step of demoting Pluto as a planet. The new rules specifically exclude the Kuiper belt object Sedna, giving the impression that (despite the inclusion of Charon) they’re setting up Pluto as the lower limit for a celestial object to receive planetary status — closing the door after the horses have bolted, as it were.

There’s something a little wrong with science that they’re willing to bend the rules in order to avoid the truth. The truth may be, comparing the orbits of Pluto, Charon and Xena with the eight larger planets, that our solar system has eight planets, not nine, but we still want to cling to the truth as we’ve known it since 1930.

And I have to ask: what separates the Moon from Charon? If Charon is a planet and not Pluto’s moon, then why isn’t the Moon itself a planet, given that it’s bigger than both of Pluto and Charon put together?

Still, I think it’s great to find this story on the front pages of newspapers all across the world. In this age where conflicts and destruction dominate the headlines, how rare is it for us to look up?

So: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Xena. — Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Xena.

Talk about your mouthful.

I should note that “Xena” is only the unofficial name of 2003 UB313 and, if it is named as a planet, the leading contender is Persephone. Not a bad name; I could go for that.

Oh, and I could not help but laugh at this:

“We have been living with Pluto as a member of the solar system for 76 years, and school children just love Pluto and we can’t take it away from them or they will be broken-hearted,” conceded Owen Gingerich, who chaired an International Astronomical Union committee on the matter.

Translation: “The children! The children! Won’t somebody please think of the children!”


If the decision to up the number of planets in our solar system to twelve holds, I wonder if writers Kit Pedlar and Gerry Davis are kicking themselves in the great beyond. They penned the first ever Cyberman story of Doctor Who, which established (Warning: bad science ahead) that the creatures came from an Earth-like planet (called Mondas) that shared our orbit around the sun before it broke off and went skittering out of our solar system (read here and here for a full explanation and the dramatic implications being raised). The inhabitants of that planet converted their biological bodies into mechanical parts in order to avoid extinction in the cold reaches of outer space.

The reason why I say that they might be kicking ourselves that the IAU’s decision didn’t come before 1966 is because they titled their story “The Tenth Planet”. Had Ceres, Charon and Xena been part of the mix, they could have entitled their story “The Thirteenth Planet” or “Planet 13” and given their story a title with a lot more sinister cachet.

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