Hubble finds Pluto's 5th "moon"
- Thread starter Ar-Pharazon
- Start date
Pluto's just trying to make itself relevant again after being demoted. 
That's no moon; it's a....
There are plenty of small asteroidal moons around the outer planets, not to mention Mars. I'd say anything large enough to be called an asteroid (or technically, minor planet, since "asteroid" is not formally used for anything beyond Jupiter's orbit of the Sun) could be called a moon so long as it's in orbit of a more massive body.
I think what you mean to ask is whether there's a minimum size a primary has to be in order for its satellites to be called moons. But apparently there isn't; over 200 minor planets are known to have natural satellites, and it appears to be valid to call them moons, so long as they're significantly smaller than their primaries: http://en.wikipedia.org/wiki/Minor-planet_moon
A what? A Howard Johnsons? A Dennys? Tell us!
Also, Christopher, yes that's what I was asking about. Planets now have certain criteria to meet to be considered a planet, I think moons should have something similar.
If they restricted what a "moon" is, Jupiter would have a lot less of them.
Why? That seems to needlessly overcomplicate things.
Really small moons are sometimes called moonlets, but that's informal.
IIRC the asteroid Ida has a moon, Dactyl, which I think is just over a mile across. It's confusing enough that a dwarf planet cannot be a planet but it can be a dwarf planet AND a plutoid, why do it to moons to.
It'll be interesting to see what they find when New Horizons gets closer, I know there is some concern there could be some smaller debris around Pluto that could be hazardous to the probe. 2015'll be fun, Dawn will arrive at Ceres that year too, that should be interesting as well.
Yeah, I think the IAU definition is very flawed due to the politics behind it. I like the dwarf planet category, but it makes no sense to say a dwarf planet isn't a planet, given that a dwarf star is still a star, a dwarf galaxy is still a galaxy, etc. (A dwarf kiss is still a kiss?)
Pluto is a fucking planet. Deal. 
"What is a moon" could be a good question.
As pointed out there's plenty of asteroids that have smaller asteroids orbiting them. Are these smaller asteroids "moons"?
As pointed out there's plenty of asteroids that have smaller asteroids orbiting them. Are these smaller asteroids "moons"?
Knight Templar
Commodore
Wasn't Pluto a planet again in the 24th century before an overlarge (and poorly written) Borg Cube consumed it in an awful Peter David novel?
There is a long Wikipedia article that basically says there is no size limit and a moon is just any body that's caught in another's field of gravity and kept in an orbit by it.
There are rather a lot of photos of moons there as well.
http://en.wikipedia.org/wiki/Natural_satellite
Personally, I tend to consider round ones moons while irregularly shaped ones are more like asteroids that accidentially got caught and therefore don't really count. But that's no official scientific opinion, just my gut feeling
There are rather a lot of photos of moons there as well.
http://en.wikipedia.org/wiki/Natural_satellite
Personally, I tend to consider round ones moons while irregularly shaped ones are more like asteroids that accidentially got caught and therefore don't really count. But that's no official scientific opinion, just my gut feeling
^But that would exclude most of the moons in the Solar System. Besides, some moons are large enough to be called planets if they weren't in orbit of larger bodies. So if you're going to call planetlike bodies moons, there's no reason not to call asteroidlike bodies moons too.
As I've pointed out many times before, it wasn't about politics as much as it was educational expedience. Grade school teachers -- most of whom find astronomy HORRIBLY boring -- have a hard enough time just teaching the names of the major planets. Adding pluto as a planet meant also recognizing Ceres and god knows what else might be lurking out there in the kuiper belt. THe IAU figured it would be easier to restrict "planet" to mean the eight major planets that school kids will learn about and "dwarf planet" to be in a separate category altogether.
They did a similar thing with the continents, by the way. In exactly the same way, and for mostly the same reasons, we have seven named and distinct landmasses, many of which have entirely arbitrary boundaries, but were so named -- and so taught -- simply to keep things simple for children.
^ Source?
If that's true (and I've never heard it before, so I'd also like to know your source), that sure sounds like politics to me -- doing something because it suits some agenda or public-relations consideration rather than because of the science.
I don't think so. The only actually arbitrary boundary between continents is the one between Europe and Asia, and that one only exists because Europeans were making the maps and wanted to call their land a continent of its own, even though by all rights it's just the western tail end of Eurasia, like Siberia is the eastern one. But the borders of Eurasia, Africa, the Americas, Australia, and Antarctica are almost entirely ocean, and the dividing lines between the Americas and between Africa and Eurasia are pretty much the narrowest points of contact between them, though maybe politics did have some influence on exactly where the lines were drawn on the fine scale.
Really, if simplicity were the prime concern, then we would've long since dropped the conceit that Europe is a distinct continent and just gone with six instead of seven.
I respectfully disagree. The Ural mountains, official border between Asia and Europe, are pretty much the seam of the continental shelves as well. On topographical maps you can see rather nicely how the European shelf gets pushed into the Asian one (by the African shelf, btw) and raises these mountains:
http://en.wikipedia.org/wiki/File:Russland_topo.png
On this satellite pic it's even more clearly visible: http://novaonline.nvcc.edu/eli/evans/HIS241/Notes/Geography/Urals.html
Strictly speaking though, Asia would have to be divided into 2 continents as the Indian subcontinent is pushing north, folding up the Himalayan, exactly like Africa pushes into Europe, folding up the Alps.
Perhaps it'd be generally a good idea to divide the planet up according to shelves. Traditions are all good and nice but when they turn out to be inaccurate they should be given up. After all, hardly anyone nowadays would incinerate redheads on the stakes, even though for a few centuries that was a rather popular pastime..
And - here we get back to the moon and planet definition - perhaps it was time to reform the definition of 'planet' as well. Though I do feel a little sorry for Pluto, Quaoar, Sedna, Orcus and Xena.
But hey, they are still orbiting the same sun as we do, so whatever you call them, they are always part of the family
http://en.wikipedia.org/wiki/File:Russland_topo.png
On this satellite pic it's even more clearly visible: http://novaonline.nvcc.edu/eli/evans/HIS241/Notes/Geography/Urals.html
Strictly speaking though, Asia would have to be divided into 2 continents as the Indian subcontinent is pushing north, folding up the Himalayan, exactly like Africa pushes into Europe, folding up the Alps.
Perhaps it'd be generally a good idea to divide the planet up according to shelves. Traditions are all good and nice but when they turn out to be inaccurate they should be given up. After all, hardly anyone nowadays would incinerate redheads on the stakes, even though for a few centuries that was a rather popular pastime..
And - here we get back to the moon and planet definition - perhaps it was time to reform the definition of 'planet' as well. Though I do feel a little sorry for Pluto, Quaoar, Sedna, Orcus and Xena.
But hey, they are still orbiting the same sun as we do, so whatever you call them, they are always part of the family
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