Revived question: Is Pluto a planet?

It hasn’t cleared the neighborhood around its orbit, meaning it doesn’t have enough gravity to impact, collect as a moon, or slingshot out all of the debris out where it is. If we call Pluto a planet, we logically have to call a lot of other debris planets and that would reduce the utility of the word to astronomers.

And if frogs had jetpacks, they wouldn’t bump their asses hoppin’. Is there any reasonable mechanism that could put something the size and composition of the Earth all the way out there?

It was a vote held among qualified members of the relevant field, not ignorant members of the general public. That isn’t really a popular vote at all, and it certainly isn’t one ruled by ignorant passions.

If you moved the Earth close to Jupiter, travelling at the right speed in the right direction, the Earth would become a satellite of Jupiter, and would no longer be a planet. What’s wrong with that?

And if Ceres and Mercury (through some miracle) were to swap places, then Ceres would become a planet, and Mercury would stop being a planet.

It’s not just size and mass of the object: it’s their orbital status and their relationship to other objects in their neighbourhgood.

You’re missing the point. If there was an object out around Pluto the exact same size as the Earth, it wouldn’t meet the definition of a planet due to it failing to sweep its orbital path of debris. Two objects the same size, orbiting the same sun, should be classified the same, don’t you think?

Jupiter, Earth and the other 8 planets also have roughly circular orbits in the plane of the ecliptic. Pluto’s orbit is more elongated and much more tilted to the ecliptic than the rest.

I count just six other planets: Mercury, Venus, Mars, Saturn, Uranus and Neptune. Which are the other two?

Planet X and Bizarro Krypton. Duh.

You’re calling Phil Plait ignorant now?

It seems to me that Pluto does a fair amount of waddling and quacking, and most educated people alive grew up believing it was a planet, so what’s the harm in allowing it to stay a planet? It’s not like the definition of a planet is so firmly set that mathematics or sciences depends on it. It’s a descriptor that in this context has very little importance.

The first problem is that a lot of new planet-like objects are being discovered these days, in orbits around the Sun beyond Neptune’s orbit, and it’s nice to be able to say whether each of these is a planet or not. So it’s useful to have a definition of “planet”.

The second problem is that it’s hard to have a definition of “planet” which includes Pluto (which most people though was a planet for 70 or so years), and which does not include Ceres (which has not been thought to be a planet for around 200 years).

Fine. You have your 2006 definition, but Pluto is grandfathered in.

This is more of a debate than a factual question, but science is a field where errors should really not be grandfathered in.

Sorry. I’ve been in GD a lot lately.

But I like Pluto.

Which is why geophysicists have voted on dropping Europe from the list of continents.

Make it fair. Define Pluto to be a continent and everyone can go home happy.

THen does Europe get to be a planet?

As opposed to “the trans-Neptunian peninsular appendage of the Solar System”? :slight_smile:

Pluto has moons, Ceres does not(while a planet doesn’t require a moon(s), having a moon(s) is one of the indicators of “planetness” IMO(unless the body is already the moon of another, larger body)).

Pluto has a diameter of more than 2000km, Ceres is less than 1000km in diameter. Set up a size requirement.
Of course, using those definitions Eris becomes the 10th planet, but I have no problem with that. This whole stupid redefinition came about because for some reason astronomers didn’t want to classify Eris a planet*, and they nicked Pluto in their efforts not to do so. Stupid.
*The only reason I’ve heard is “Well, their may be more bodies out there that meet the definition of planets unless we change it”. So? If we wind up with 20 planets, or 12, or 3567, who cares?

But Makemake is right out without a name change. I’m sorry, but with every other planetary body in the solar system being either Roman or Greek, don’t try throwing in Easter Island on me.