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25 August 2006 @ 06:31 am
Pluto: for and against planethood  
So, Pluto has officially been demoted to status of "Dwarf Planet", which in my opinion is a bit of a half-assed compromise name, because along with that astronomers are making the announcement that Pluto is no longer a "planet". And, of course, people are bitching and moaning about it. So here is my brief summary of the arguments for and against Pluto being a planet.


  • It is absolutely tiny compared to the other planets.

  • It is made of ice, rather like a comet.

  • Its "moon" is about the same size, and they actually orbit around each other.

  • Its orbit is tilted relative to all other planets in the solar system.

  • If Pluto is a planet there are at least three chunks of ice that need to be reclassified as planets, plus almost certainly dozens more in the Kuiper belt, probably hundreds, possibly thousands. (Does it not diminish the value of the term "planet" if there are thousands of tiny balls of ice in all kinds of crazy orbits given that classification?)

  • Failing the reclassification of the other ice-balls, it is confusing and scientifically unhelpful having two different classifications for the same type of celestial body.

  • And one that I think there is some confusion surrounding: Pluto doesn't exert enough gravitational force to have been able to carve out its own clear orbital path around the sun. The confusion here is in thinking that this is about Pluto's orbit crossing Neptune's. Sure, maybe that's part of it, but the main point, really, is that Pluto's gravity is not strong enough to have diverted (or attracted) a number of comets that travel through its orbital path.


  • It's "always" been called a planet.

  • People want it to be a planet.

  • People don't want to have to explain to their poor easily-traumatised children that Pluto is no longer a planet (heaven forbid they should actually have to explain and discuss the issues with their kids; oh no, kids aren't capable of understanding the science behind it, they'll just be sad about "losing" Pluto).

  • Textbooks will have to be reprinted (funny, I seem to remember textbooks being revised almost annually when I was in school).

  • We'll have to come up with new mnemonics (and the completely stupid and false corollary that the new mnemonics will somehow be inferior to the old ones).

  • It's got the same name as a cute cartoon dog (never mind that Pluto is the most annoying in a painfully annoying cast of characters).

Seriously, people, get over it. Pluto isn't a planet. It never was a planet. It's barely more than a comet.

But, more importantly, this ruling brings Pluto (and its dwarf planet brethren) into the spotlight. Calling Pluto the furthest, smallest planet was doing it a disservice, because that meant that there was not enough acknowledgement of its real differences compared to the other planets (which are, of course, themselves divided into two very different categories). Now the story of Pluto's rise and fall in status will generate discussion of not just the basic concept of planets, but the deeper issues of the many known and unknown objects in the greater solar system. This "demotion" brings with it a sense of wonder: if Pluto is just one object among many, what is yet to be found in the little explored outer reaches of our solar system?
Tags: ,
Current Music: Pink Floyd - Astronomy Domine
proxyryanproxyryan on August 24th, 2006 10:35 pm (UTC)
will generate discussion... brings with it a sense of wonder

I think you're being a shade too optimistic about the average human here.
Some guy called Lap?harkon on August 24th, 2006 11:37 pm (UTC)
Lol, I was going to a comment that had a similar point. Except mine was more crude and involved monkeys.
Jacobyak_boy on August 25th, 2006 01:10 am (UTC)
Well, amongst those that matter then. The average human is lucky if he manages to learn that fire is ouchy.
(Deleted comment)
Jacobyak_boy on August 25th, 2006 01:09 am (UTC)
It is a fair point that the title doesn't rally matter. It is what it is. Still, I think classifications are somewhat important, if only so that young students can more easily grasp that Pluto is an object not like Earth, but like the other Kuiper belt iceballs.
Gregpeachofpain on August 25th, 2006 04:15 am (UTC)
And in today's latest news, the IAU has reached a verdict on the fallout of the orbit fixing scandal that made headlines several weeks ago. Pluto had apparently been colluding with other orbiting bodies in the solar system to obtain favourable orbital trajectories. Today's deliberations concluded with the punishment for Pluto's illegal activity being finalised. It has been confermed that Pluto is to be relegated to the second division, a move sure to cause a shake up in that league. Already there are rumours that one of Pluto's key players, Charon, may be breaking away from the team that it has called home for the last 76 years.
Jacobyak_boy on August 25th, 2006 04:18 am (UTC)
bare_feetedbare_feeted on August 25th, 2006 05:00 am (UTC)
but but... i can't be a scorpio without a planet!!!!! what about charon what's going on? the indignity of it all! humph!

Jacobyak_boy on August 25th, 2006 05:10 am (UTC)
Actually it's all good news for Charon, as it gets upgraded to the same category of "dwarf planet".
bare_feetedbare_feeted on August 25th, 2006 05:17 am (UTC)
poo! boo hoo! i miss my planet!

Jacobyak_boy on August 25th, 2006 05:34 am (UTC)
There, there.
bare_feetedbare_feeted on August 25th, 2006 11:36 pm (UTC)

Jacobyak_boy on August 26th, 2006 12:14 am (UTC)
bare_feetedbare_feeted on August 26th, 2006 12:43 am (UTC)
you've lost me.
Jacobyak_boy on August 26th, 2006 12:46 am (UTC)
–verb (used without object) Informal.
1. to glide, move, or proceed easily or nonchalantly: She just sashayed in as if she owned the place.
2. to chassé in dancing.
bare_feetedbare_feeted on August 26th, 2006 01:01 am (UTC)


Jacobyak_boy on August 26th, 2006 02:42 am (UTC)
Aww... don't cry.
(Anonymous) on August 25th, 2006 11:28 am (UTC)
I have a simple critera for whether something is a planet or not.
Do I want to go there?
Jacobyak_boy on August 25th, 2006 12:42 pm (UTC)
That doesn't leave too many planets.
Pretty much Earth and maybe Mars.
Some guy called Lap?: Urkharkon on August 25th, 2006 01:12 pm (UTC)
You left out Uranus, harr harr harr.