Two New Saturnian Moons

Mixel writes "NASA's Cassini spacecraft, which has been orbiting saturn since the 30th of June has uncovered two previously unknown bodies. 'The moons are approximately 3 kilometers (2 miles) and 4 kilometers (2.5 miles) across -- smaller than the city of Boulder, Colorado.' The Huygens probe will be deployed to the large (bigger than Mercury!) yet mysterious moon, Titan, in December."

Comments

No information about composition?

[Dthoma]

I'm aware that something that size would almost certainly be totally rocky with next to no atmosphere, but the article doesn't say whether these are gaseous or not. Surely we need to know their composition before sending a probe?

Can these really be called moons?

[Anonymous Coward]

For something so small, "moon" seems to be a quite grandiose term.

Re:Can these really be called moons?

[CrowScape]

Slight problem with your definition: Sedna is not a planet. A small planet is just that; a planet. A planetoid would be an object that wasn't good enough to be called a planet, but came close, such as Ceres. Sure, it's round, but it doesn't possess the majority of the mass in a similar orbit, so not a planet.

Millions of Moons

[Tablizer]

Saturn actually has millions of moons if you count the boulders in the rings. If you don't count them, then where is the cut-off point? This debate has never been settled, and may require an arbitrary cut-off size to get a clean definition.

Re:Millions of Moons

[Anonymous Coward]

The cut-off point is the size that is large enough to resolve individually. Thus the cut-off point changes as technology improves.

Re:Millions of Moons

[rokzy]

there's a problem at the other end of the scale too: our moon, the Moon, is so big that the Earth-Moon system could/should be considered a double-planet system.

there was a great article in the recent New Scientist about how the moon formed - a Mars-sized planet called Theia smashed into the Earth and the light rocks flung away formed the Moon.

Re:Millions of Moons

[Tablizer]

there's a problem at the other end of the scale too: our moon, the Moon, is so big that the Earth-Moon system could/should be considered a double-planet system.

I have heard a pretty good definition with the average center of orbit between the two bodies being inside the body of one of the pair. Our moon barely cuts it as a moon under this definition, but does, IIRC. However, such a definition does not work well with gasious planets since their boundary is fuzzy. But, it works pretty good with rocky bodies, at least fairly round ones.

Are they really moons?

[Anti Frozt]

Where do we draw the line between classifying a stellar body as a moon or an asteroid? Do we simply base it on the fact that it's a piece of rock orbiting a planet or is there some other defining characteristic?

Ceres, the largest asteroid in our solar system, has a diameter ~950 Km in length, much larger than many of the so-called moons we've discovered.

Re:Are they really moons?

[FLAGGR]

There's alot of debate on that, some people don't even think pluto should be considered a planet. A good way to classify it is: Planet - A really big rock with a sane orbit around a star Moon - A smaller rock orbiting a planet Comet - a rock with a highly ecentric orbit Asteroid - a tiny rock that isn't in perfect orbit with a planet, or is just floating around orbiting the sun or something. I guess the scientists like to say they've discovered moons, because discovering asteroids sounds much less cooler. I know *I* would call them moons ;)

Re:Are they really moons?

[Conch]

There is actually a limit uppwards. It's no longer a moon if the center of gravity for the planet and the moon are outside of the planet. In this astronomical sense is our moon actually not a moon but the earth and the moon make up a bi-planatery system.

What about garbage?

[www.sorehands.com]

If we throw a trashbag out of the the ISS does that become a moon? What about a bolt that is dropped when repairing a sattelite?

There must be some definition of a moon that includes some reasonable minimums -- like gravity or magnetic field.

Re-discovered?

[Mick Ohrberg]

It seems like one (S/2004 S1) of the little worldlets may have been re-discovered since it may have been spotted when one of the Voyager probes passed Jupiter by in 1981, then christened S/1981 S14.

Damn; nobody RFTA?

[Anonymous Coward]

1) I have to muse, when did Boulder CO become a unit of astronomical significance (and for the trolls: how many library of congress is that?)

2) Everybody keeps asking, but the reason these are significant is because

a) they orbit saturn (most asteroids orbit the sun)

b) they differ from the asteroids in the asteroid belt because, well, they are not in the asteroid belt

c) their orbit are actually located between two other moons, which is surprising because such area is under heavy bombarbment from other sun-orbiting asteroids and they should have been destroyed long time ago - this sheds light on our understanding of the kuniper belt, asteroids, saturnic satellite formation, etc etc.

That said, I couldn't make out the things on the picture, so i dunno... could be CCD noise? that would badly suck...

Now wait a second...

[rarose]

What if the gravity is strong enough for a suicidally depressed person to walk on, but weak enough that a happy person with a little "bounce" in their walk goes flying off into orbit?

Of course the thought of that would be enough to make any astronaut upset.... so... wait... I guess that won't be a problem.

But where did the RING SPOKES go?

[Wraithlyn]

The last time Saturn was visited, it had these "spokes" visible in the rings. Now, they're nowhere to be seen.

This report: http://www.enterprisemission.com/_articles/05-27-2 004_Interplanetary_Part_2/InterplanetaryDayAfter-P art2.htm

Lists a large number of rather extraordinary changes that EVERY PLANET in the solar system has gone through in the last couple decades.

Personally I find it rather alarming. Massive oxygen appearing on Venus? Io hotter than Mercury? Radical new weather patterns on Neptune, and even Pluto? The gas giants radiating vastly more energy than they receive from the Sun?

Is this guy onto something big, or is he delusional?

Re:But where did the RING SPOKES go?

[Wraithlyn]

I have read a great deal of his stuff, and his critics too. I am not talking about his THEORIES though, I am talking about his OBSERVATIONS, specifically concerning the planets in the solar system.

I checked into a few of his planetary findings (including Saturn's now missing ring spokes), and they checked out as advertised. Mars' ice caps are dissapearing rapidly, and had a 3 month long global dust storm a few years back. Solar activity is insane.. more sunspots in the last 40 years than the previous 1150. There's stuff like this described for every single planet. I haven't checked them ALL out myself yet, but the claims have been disturbingly true so far...

Re:A couple of definitions

[Scarblac]

A planet is an object massive enough to become spherical under its own gravitationnal field, that orbits a star.

Although this is a very logical definition, it's not the one that's usually used. Quite a few objects have already been found that are large enough to become spherical (Ceres, Quaoar, "Sedna", Ixion, to name a few) that aren't classified as planets.

It seems that the definition of a planet in this solar system is "those nine objects we currently call planets, and nothing else."

Re:One small step...

[uberdave]

Actually, what struck me about the sizes quoted, is that Boulder Colorado must be really small. I do a three km walk every day. I always pictured it as a big city, but you could walk from one end to the other in an hour, hour and a half. That's not a city, that's a town.

Re:What is a Moon?

[Concerned Onlooker]

Not exactly related to parent, but to the article in general, you can listen to Cassini encountering the electo-magnetic bow shock as it approached Saturn here. There are also a bunch of other cool space sounds at this site.