Wednesday, August 19, 2009

Why Pluto isn't a planet!

I'm a bit annoyed by the (again) upcoming discussion about this, so I'll quote some numbers here.
One of the most important (and impressive) numbers on the subject is the so-called Stern-Levison parameter Λ. Basically this is the ratio between the mass of an object and the total mass of all the objects on it's orbit. When you compare the numbers in the wikipedia table linked below, you will easily see that there is a fundamental difference between what (most) scientists call a 'planet' and what (again most) scientists call a plutoid or an asteroid.
Please everyone, accept that Pluto is something different. This has nothing to do with scientists not 'liking' pluto or being 'anti-american' (Yes, seriously, I read that this would be the case because pluto is the only former planet that had been discovered by an american. And indeed, the community that wants pluto to remain a planet seems to be much stronger in america). I also read about one article suggesting to abandon the word 'planet' altogether and rather use 'earth-like/rocky planet', 'gas-giant planet' and 'plutoid', I second that. Gas-giants and earth-like planets are something different still.

Now, the Stern-Levison parameter Λ for most of the big objects in the solar system (btw, something orbiting another object in the solar system than the sun, is a moon, independent of it's size, shape and other parameters) can be found here.

1 comment:

  1. I've said it before and I'll say it again... A dwarf star is a star. Why is a dwarf planet not a planet?

    After all, there are three classes of star (massive, middleweight and low mass) which structurally very different. Why not three equally different classes of planet?

    (Just my opinion :)