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Tom Mazanec
2007-Nov-12, 05:03 PM
Which moons would be dwarf planets if they orbited the sun independantly?

Warren Platts
2007-Nov-12, 05:10 PM
They would count as dwarf planets if they had enough gravity to make themselves round.

laurele
2007-Nov-12, 06:11 PM
Which moons would be dwarf planets if they orbited the sun independantly?

Since the distinction between "dwarf planets" and "planets" is still very much up in the air and unresolved, this becomes a very difficult question to answer. Any moon that is round, if it orbited the sun independently, would be categorized by some astronomers as a "dwarf planet" if it didn't "clear its orbit" and as a full fledged planet by those who reject this definition.

If the moon orbited the sun independently and was not round, i.e., has not achieved hydrostatic equilibrium, it would be neither a "dwarf planet" nor a "planet" but simply an asteroid.

grant hutchison
2007-Nov-12, 06:19 PM
If the moon orbited the sun independently and was not round, i.e., has not achieved hydrostatic equilibrium, it would be neither a "dwarf planet" nor a "planet" but simply an asteroid.If we are to stick with the Resolution 5A definitions (which seems to be the OP's intention), then such an object would fall into category 3, and would be a small solar-system body. It might then be subclassified according to its structure and orbit, asteroid being one possible category.

Grant Hutchison

aurora
2007-Nov-12, 06:35 PM
Which moons would be dwarf planets if they orbited the sun independantly?

Let's see...

Luna. Io, Europa, Ganymede, Callisto. Titan. Triton.

That's the biggies off the top of my head.

Would have to look up statistics or images of the other moons of Saturn, and moons of Uranus. I'm guessing there's another half dozen that would qualify?

Warren Platts
2007-Nov-12, 06:38 PM
Let's see...

Luna. Io, Europa, Ganymede, Callisto. Titan. Triton.

That's the biggies off the top of my head.

Would have to look up statistics or images of the other moons of Saturn, and moons of Uranus. I'm guessing there's another half dozen that would qualify?

Since most of those are bigger than Mercury, they would have to count as regular planets.

aurora
2007-Nov-12, 06:44 PM
Since most of those are bigger than Mercury, they would have to count as regular planets.


Is that the criteria?

If so, then Ganymede and Titan both have a larger diameter than Mercury, and Callisto has essentially the same diameter as Mercury. So I guess they wouldn't be dwarf planets.

But Luna and Triton and Io and Europa are all smaller. So I guess they would be.

Trantor
2007-Nov-12, 06:47 PM
Let's see...

Luna. Io, Europa, Ganymede, Callisto. Titan. Triton.


I think that both Ganymede and Titan would be considered a planet if they had an independent orbit. Both are larger than the planet Mercury. Even Callisto might be considered a planet, as it's only slightly smaller than Mercury.

grant hutchison
2007-Nov-12, 07:24 PM
Since most of those are bigger than Mercury, they would have to count as regular planets.The criterion for planethood is based on "orbital clearance", which requires some sort of evolutionary process to take place. There is no size criterion, except that the object must be big enough to settle into hydrostatic equilibrium -- the same rule as for dwarf planets.

So the planet / dwarf planet division is undecidable, given the scenario in the OP.

Grant Hutchison

Noclevername
2007-Nov-12, 08:01 PM
The naming conventions are arbitrary; I propose replacing them with a "planetary spectrum", gradually going from microscopic dust --or gas molecules!-- to stars of equal mass to their primary.