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

hmmm

[happy monday]

uranus... moon... i know there's a joke in there somewhere...

Re:hmmm

[L. VeGas]

or black holes

dammit

[austad]

I found that the other night also, time for a trip to the doctor.

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?

[Anonymous Coward]

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?

The L4, L5 points of what exactly? Of the solar system? I hate to be the one to break this to you, but there are just a few more than two masses floating around out there. Lagrange points only apply to the two body problem, any more than that and the dynamics become incredibly complex.

Mercury's a tiny little thing that would be lucky if it could capture my desk much less a sizeable mass (exaggeration). Mars is large but still rather puny though you should note that it does have moons of its own, more than us though they are smaller. Venus could hold something like our moon, but apparently the crapshoot of the universe favored Earth instead.

Outside the belt, we've got bloody HUGE planets compared to the dinky inner pebbles. Pretty much any rock floating around can be captured by them (as long as its solar orbit is not too extreme) but in comparison there are plenty of bodies that could never be captured by an inner planet no matter the orbit.

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.

Re:farther out = more moons?

[caffeinated_bunsen]

Time to check again - the planetary masses have changed quite a bit since your last look. Jupiter is about 3.4 (not 50) times the mass of Saturn, and about 318 (not 1000) times that of Earth.

(Data from here, specifically these pages.)

Re:farther out = more moons?

[Bonker]

It's been theorized that the only reason that Terra has a moon is because early in our planet's development, it was split in two large chunks by a planetoid impact.

An early protoplanet slammed into Earth, vaporizing rock, etc... The force of the impact ejected a large part of the Earth's mass. It eventually cooled and settled into its own suborbit around the reforming earth.

This theory has been propped up somewhat by analaysis of the Moon's structure. Luna seems to be composed of rock like you would find in the Earth's mantle, but has a noticeable lack of a magnetic or electrical field, indicating that it doesn't have a lot of iron or nickel, which you would expect to find if it had formed independantly of Earth.

Bottom line-- The moon has the highest ratio of mass to its parent body as than any other moon in the Solar system. If we didn't arbitrarily consider Luna a moon, it would be a lot more correct to say that the Earth-Moon system was a dual planetoid system and not a planet-moon system.

Re:farther out = more moons?

[phriedom]

That makes sense, but your example Triton orbits Neptune which only has 8 moons compared with 39 for Jupiter, 30 for Saturn, and 21 now for Uranus. It seems like Neptune should have more moons than Uranus, since it is a gas giant, it is larger, and it is further from the influences of the Sun and Jupiter. Uranus is also odd in that its orbit is twisted on its side, but most of its moons share the same plane, which leads me to believe that most of them were not captured. Can someone shed some light on this subject?

My only idea is that Triton, which is pretty big as moons go, and an order of magnitude more massive than anything around Uranus may have knocked smaller moons of Neptune out of orbit when it arrived. But what do I know.

Re:farther out = more moons?

[CheshireCatCO]

The moons of Uranus probably are in the equatorial plane thanks to effects of Uranus's not-quite-spherical shape. Most moons will head towards the equatorial plane in time, even captured ones.

What you are (possibly) forgetting about Neptune is that being farther from the Sun makes it also farther from the Earth. Finding moonsa around Neptune is even more difficult than finding them around Uranus (which is in turn more difficult than finding them around Saturn, etc). Besides being farther away from us, the light out there dimmer. (Neptune is about half-again as far from the Sun as Uranus, which translates to leass than 1/2 the light per area.) Before deducing much about the relative numbers and what they mean, I think we should wait for significantly more complete satellite searches around all 4 giant planets.

Of course, you might be right. Neptune might have fewer moons in the end. Then it could be because of Triton (being both very massive and in an irregular orbit might make it an impedment to other moons' existences). There might also be other effects. Or maybe I was over-generalizing the processes. But I'm not ready to start worrying yet.

Re:farther out = more moons?

[whovian]

There is another way to look at it: Consider that the bodies that we call the inner "planets" are simply moons of Sol as it revolves around the galactic center.

Relative motion has its idiosyncrasies.

Urectum..?

[Scaba]

I thought they changed the name of Uranus to Urectum because all of the jokes...

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...

Caring

[Trusty Penfold]

Are astronomers ever going to stop caring about new satellites? If so, when?

It is obvious that there is all sorts of stuff floating around the solar system, some of which is in orbit around other non-solar objects.

Does knowledge about a 21st moon of a remote planet really increase our understanding of anything?

Re:Caring

[redcliffe]

Some of these are captured Kuiper belt objects, which are very interesting. Also when we have ships that can go out there, we need to know where these things are so we don't smash into them.

Re:Caring

[CheshireCatCO]

Does knowledge about a 21st moon of a remote planet really increase our understanding of anything?

I know. As a matter of fact, it does. If we only had a handful of moons to look at, we'd never really know to what extent the trends we see are just statistics of a few and to what extent they reflect real underlying physical processes at work. Each additional moon adds to the statistics. Individually they aren't wildly important. Collectively, larger numers of moons lead to better theories of where this little guys come from. Brett Gladman, who received the annual Urey Prize for the Division for Planetary Sciences this year, gave a talk about irregular satellites. Having been in the audience, I can tell you that having many moons on there made the trends a lot more believeable than had there been only, say, 5 data points.

If you're asking if each new moon is worth of a headline or even a Slashdot story, I'd agree that it really isn't. But if you're wondering if we should bother looking for these moons, I'd have to say yes, absolutely.

Size

[isorox]

The moon ... is between six and 12 miles across.

Wow. In 100 years we'll have space stations that big. it's hardly Moon (x00miles+) size is it? Y'know theres a golf ball floating arround the Earth's moon - a moon of a moon?

Re:Size

[mgblst]

That's no moon....its a space station.

no jokes ... please

[tswinzig]

Uranus is no laughing matter!

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.

It's not pronounced "your anus"

[GCP]

The preferred pronunciation is "urinous", class. "Urinous". So, see, there's really nothing to snicker about. Class? That's enough now.

your anus

[Transcendent]

[insert joke in relation to someones abnormally large buttox]

[auto-mod +3: Funny]

Are they sure...

[kaimiike1970]

That it isn't a really big kernal of corn? I mean those things go right through me.