New Moon of Uranus Discovered

paulnuyu writes "A group of international astronomers have found a new moon orbitting Uranus. This brings Uranus's total moon count to 21. The newly discovered moon is speculated to be a remaining fragment from a collision that occured when the solar sytem was still forming."

Comments

farther out = more moons?

[Hadlock]

it seems that mars, venus, & mercury all have few or no moons, while on the other side of the asteroid belt, you have planets (sans pluto & really small planets) with moons in the teens to twenty in numbers. why is this?

is most of the space matter in our solar system stuck in the L4, L5 points, and thus doesn't find it's way into the inner regions of the solar system? or is it just that the enormous mass of the farther out planets seems to attract more mass & thus has a higher chance of a rock entering orbit (as a result of a larger margin of error for stable orbit due to the size of the planet). it just seems to be more than coincidental....

or is it just a possiblity that these planets have a particularly large asteroid in an unstable orbit just long enough to discover and document, before it a) leaves orbit or b) gets sucked into the atmosphere?

Re:farther out = more moons?

[CheshireCatCO]

Ok, lots to say here.

I think perhaps the best way to look at the terrestrial (aka, inner) planets - moon-wise - is that they don't form with moons, so any moons we find are probably anomalous in some senses. Earth's Moon is a bit of a freak, having formed in a very stochastic even. Mars's two moons are most likely captured asteroids. Venus and Mercury are in some ways more like what I'd expect to see in a large fraction of a larger terrestrial planet population.

The outer solar system has it good, moon-wise. First off, the giant planets are thought form with accretion disks about them in the later stages. (I believe Canup and Ward have a paper coming out on this topic in Astrophysical Journal in not too long.) This makes a good place to form moons, it is thought.
It gets even better, though. The jovian planets also probably had larger gas envelopes early on, making it easier to capture a moon (like Triton). You need some way to ditch energy in order for capture to occur, and drag is a nice method.
And better still: it's easier for giant planets to affect objects in their area. Their Hill spheres (domains of gravitational dominance compared with the Sun's gravity) is larger thanks largely in part due to their greater distances from the Sun. This leaves a larger volume around them in which they can start to mess with small bodies and potentially capture them, under the right conditions.

All in all, if you want to either form (in situ) or capture a moon, the outer solar system is your best bet. It's still possible to pull some tricks in the inner solar system, but they're less likely.

Yes, I know...

[GreyWolf3000]

The article is about Uranus. I think we all know the joke, and we can all laugh about it by ourselves in the privacy of our own desks, without posting lame jokes here. This dead horse is beat. Most of us (except for the moderators ;) are over 15 and can be expected to behave in at least a semi-adult fashion.

You know, on second thought, screw that crap. This joke never gets old. The more I think about "21 moons on Uranus" the more I crack up. Pun intended. Just allow yourself to laugh at this, and maybe even let it lighten up the rest of your day. It has mine.

I also can't wait until a story comes along about how scientists "find" a small chance that there could be frozen water, which could indicate the slim chance of life. In turn, there'll be all the boring threads about the seti@home project and distributed computing to look forward to--certainly more pertinent than this post of course, but what the hell...

Many Moons

[WeaponOfChoice]

I used to think it'd be cool to have more than one obviously visible moon in the sky. 21 may be a bit much but it'd certainly make the sky interesting.

Thinking about it, 21 significant orbital bodies accompanying a planet the size of our own would create nightmares for people trying to predict the tides, and we'd have to get some pretty serious seismic activity from any significant alignment.

Even worse some form of collision is almost inevitable over the full expanse of time, moons ricocheting like billiards around the sky [joking].

Give a lot of options for moon bases too - countries could argue over who gets the biggest or best situated. I guess we'd lose the use of the L points as a side effect though (or there'd be L orbits weaving monstrously complicated paths though the orbits of the moons)...

Re:Many Moons

[WeaponOfChoice]

Probably should just stick to using the term satellite. Avoids the old 'but is it [?] enough to qualify as a [?]' trap. Won't be as popular with astronomers who like to be able to claim discovery of 'significant' stellar bodies, though I agree that 'moon' insinuates some measure of significance that a 12 mile rock simply does not have. There are asteriods orders of magnitude larger that get less special treatment...

Re:And the bit from Futurama

[Syncdata]

Professor: I call it "The smelloscope". Try it!
Fry:Just don't point it at Uranus..
Professor:Very funny Fry, we changed that planets name years ago just to get rid of that stupid joke.
Fry:What did you call it?
Professor:Urectum.