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New Moon of Jupiter Discovered
Posted by
CowboyNeal
on Sat Dec 28, 2002 10:47 AM
from the heavenly-bodies dept.
from the heavenly-bodies dept.
xihr writes "Astronomers have discovered a new moon of Jupiter, bringing its known retinue of satellites to a whopping 40. The new moon, designated S/2002 J1, is only 3 km wide, and has a highly inclined and eccentric orbit.
Astronomy.com has the story."
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Questions (Score:5, Interesting)
Would it be possible haul enough of a mountain into space orbit to be technically classified as a moon? I mean, man has walked on Earth's moon.. but is he able to make one himself? Or has he already?
-Matt
Re:Questions (Score:2, Funny)
Re:Questions (Score:2)
1) If it freely orbits the Sun (or some other star, which is now becoming more than an academic distinction), and it's Pluto-size or larger, it's a planet. (To get rid of the "Pluto is not a planet" silliness.) Otherwise it's an asteroid, a comet, a Kuiper belt object, whatever.
2) If it orbits a planet orbiting the Sun (or some other star, etc.) and it's either a) larger than Phobos or Deimos (whichever is smaller, I forget) or b) larger relative to the planet it orbits than min(Phobos,Deimos) is relative to Mars, then it's a moon. Otherwise, it's a captured asteroid, or a microsatellite, or whatever. And yes, this means Earth only has one moon, and will for some time, until we build a space station larger than min(Phobos,Deimos) -- which will be a while, I gloomily suspect.
Like I said, this is completely arbitrary, but it has the advantages of both retaining historical classifications and satisfying the original version of Occam's razor. (Don't multiply entities unnecessarily.) There's a lot of stuff floating around the Solar System, and we're finding more all the time. How many damn planets and moons do we really need?
Re:Questions (Score:5, Informative)
If it freely orbits a star, is IN THAT STAR'S PLANE OF THE ECLIPTIC, it's a planet (note: this knocks Pluto off the list). You still need some arbitrary limits here, though: I'd say as long as the normalized dot product of the orbit's normal vector with the plane of the ecliptic is within four sigma, you can call it a planet (note - don't take the absolute value - if it's going the wrong way, it's not a planet). Interestingly enough, this places most of the asteroids in 'planet' status.
That pretty much limits planets to objects which were clearly formed from the accretion disk of the star, as opposed to 'leftover junk' (which something like Pluto most assuredly is). Of course, this also means that a planet can get knocked out of its original orbit, and lose its 'planet' status, but this is also an acceptable side-effect if you want definitional consistency.
For 'moon', any body which orbits a planet within two sigma of ITS plane of ecliptic should be considered a 'moon'. Here we need a good definition of 'orbit' - if, at any time, an object's orbit brings it *away* from the center of mass of its solar system, and towards its planetary primary, it's in orbit around that planetary primary, and not its star. This means, incidentally, that the Earth's Moon is not a moon - it's another planet that happens to co-orbit the sun within the same boundry space as the Earth, and the two planets perturb each other's orbits.
Any body which does not fall under this criteria is a 'satellite' of its primary, but not a 'planet' or 'moon'.
While this definition leads to a few counter-intuitive situations (or at least, counter-traditional), that's inevitable when formalizing terminology. People use words too loosely to expect all possible cases to fit the 'traditional' nomelcatures, so when formalizing, you sometimes have to accept a few deviances (for example, if we were to normalize biological taxonomy, dogs, wolves, coyotes, and jackals would all be the same species - since they're genetically capable of interreproducing. It's only weight of tradition that keeps them seperate, a very unscientific concept.)
Parent
Re:Questions (Score:2, Insightful)
This seems to be a bad and ambiguous definition and an erroneous interpretation of that definition.
1) It's circular. You definite orbit in terms of orbit.
2) The Earth is, at some point in its orbit, moving closer to the Moon and away from the sun, ergo it is the Moon's moon. And vice versa.
3) The Earth is, at some point in its orbit, moving closer to Neptune and away from the Sun, ergo it is Neptune's moon.
Surely the simple criterion is along the lines:
1) if we can see A moving around B and C, and we were to remove the influence of C, and then A continues around B, A is orbiting B -- if they would just fly off to infinity (or otherwise approximate a hyperbolic orbit) then A is not orbiting B.
2) if A and B satisfy condition 1, then we say A orbits B if A is (some degree of our choosing) less massive than B. If they are within (some degree of our choosing) we say they orbit each other.
Satellites, Moons, Humans (Score:2)
Interestingly, a whole stack of these moons were discovered around 2000 when astronomers decided to search existing photographic plates for them, then went looking for more. I remembered Jupiter have about 12. Read about it here. [arizona.edu] (An intereting solar system site in general.)
As for moon v. satellite, a moon is simply a natural satellite. Some purists say that only the Earth has a Moon (capitalized) whereas other planets such as Jupiter have natural satellites. As mentioned in the link above, "captured asteroid" is another candidate for these irregular-orbit chunks. Our Moon, meanwhile, is very unusual in the Solar System for its great size relative to its planet -- about 25% IIRC. There are bigger moons elsewhere, but the strength the gravitational Earth-Moon attraction has many dramatic effects. (I've also read that the Moon is more greatly attracted by the Sun than the Earth, thus it orbits the Sun. Please don't ask me to explain or defend, but it sounded plausible [edjohnston.com]...)
BTW -- someone suggested non-moons are distinguished by being mostly metal (e.g., Landsat) -- well, many asteroids are mostly free metal, too (Fe, Co, Pt, and so on). If you want to split hairs, most rock is made of metallic compounds (Si, Fe, etc.).
Re:Questions (Score:2)
My personal criteria would require uniqueness and stability. That is, tiny rocks in a ring are not unique, whereas a single (or two, or 40) orbiting body deserves special recognition. Also, the orbit must be stable. That is, an asteroid captured by a planet's gravity in an orbit that will smash it into something in 200 years is not a moon. It is a pet.
Re:Questions (Score:2)
Re:Questions (Score:2)
When will we have the technology to make that a serious question? Not this century, at the rate we're going.
For what it's worth, international law is that you can't create or expand a country by building an island. If the island isn't naturally above water at high tide, it doesn't count. One of Japan's boundaries depends on a tiny island a few meters across, and to keep it from wearing away, which would cost Japan fishing rights, a breakwater has been built around it.
Re:Questions (Score:5, Informative)
Anything orbiting a planet is a satelite, but not every satelite is considered a moon.
Parent
Re:Questions (Score:2, Interesting)
this is debatable, as astronomers have yet to agree on what a moon is. [space.com]
Re:Questions (Score:3, Insightful)
Re:Questions (Score:2)
Could you elaborate on this, please?
Re:Questions (Score:5, Interesting)
Astronomers and cosmologists use the term "metal" as a shorthand for anything other than hydrogen and helium.
Parent
Re:Questions (Score:3, Interesting)
Just goes to show that even scientists can fall into the trap of ambiguous contextual terminology. It'd be nice to go through and create a single, agreed-upon, interdisciplinary scientific language, where when you talk about something, everyone knows what you're saying. (While we're at it, let's set the speed of light to 1 and try and normalize as many fundamental constants as possible.)
Re:Questions (Score:2)
Why am I not surprised?
Heck, I think physics and chemistry has two opposing views on electron charge flow, and electrical engineering holds that both are true. It's pretty frustrating to deal with this sort of crap.
I think we should steal it. (Score:5, Funny)
Tell the DEA somebody is growing pot there... (Score:2)
By Jove!!! (Score:5, Funny)
By Jove, another moon!
runs away quickly
Old Joke... (Score:5, Funny)
Stupid name... (Score:5, Informative)
Re:Stupid name... (Score:2)
As much as you meant it as a joke.. It's really a damn fine suggestion.
"Cowboyneal" the 3k wide geek moon. Bet it's full of wookies.
Finally! (Score:3, Funny)
Cool money making scheme (Score:5, Funny)
"Class, this is a picture of YourMomNaked as it completes its orbit cycle."
Is Cowboy Neal wide enough to count as a moon? (Score:4, Funny)
Moons. (Score:3, Interesting)
That aside, I wonder when the folks working on Celestia [shatters.net] will release an update to display the new moon in the space similator.
Re:Moons. (Score:3, Interesting)
Well no, there's no "cutoff" size (Score:3, Interesting)
The answer in both cases is somewhat similar. A ship is a vessel large enough to carry a boat. Not very enlightening actually, if you insist on rigid taxonomy for every little object in existence. After all, a 22' sailboat can carry an 8' tender on deck, and yet remains merely a boat, not a ship.
The basic standard for being a planet is large enough to have a moon. Uh huh. Cue the self referencial infinate loop here.
Although Pluto meets, barely, this standard, quietly in the backrooms it isn't even really considered a planet these days. If we knew as much about it in the 30's it probably never would have been classified as a planet in the first place. "Planet" is also largely considered to only apply to those major bodies that were formed as such with the solar system. Circumstancial evidenced suggests that Pluto started "life" as a moon of Neptune that "got away," possibly knocked out of orbit by a comet.
That would mean Pluto is a planet that's *also* a moom, although without being a planetary satellite. It's a weird dude, dude.
The only rule for being considered a moon is being "big enough" to be so classified. Uh huh. Cue thumb up nose routine here.
The rule of, ummmmmmmmm, thumb, is if you can walk around on it it's a moon. Unless it isn't rocky, we're prejudiced against ice balls. Or maybe if it's discovered on Tuesday. Who knows?
Of course most of these small moons of the gas giants wouldn't even come close to meeting the formed naturally in the system test. They're pretty much space junk that's ended up stuck in the planet's gravitational field as they wandered by. Captured asteroids. Cue video game joke here.
Of course if you could literally anthropomorphise a bit of space rock and ask it what it was ( which I don't recommend because they hate that) it would almost certainly say, "Yahwe, now bugger off." It is what it is, and that's all that it is.
This urge to rigidly classify everything is a human failing. The rocks themselves couldn't care less.
KFG
Just Another Captured Asteroid (Score:5, Informative)
BTW, the rings of Jupiter are close to the planet - this new moon is not. It's so far away you couldn't see it with the naked eye if you were so unwise as to stand on the surface of Europa or Io and look for it.
Re:Just Another Captured Asteroid (Score:2)
Could this be a recent moon? (Score:3, Interesting)
*checks*
Hmmm, no smoke yet.
Re:Could this be a recent moon? (Score:2)
Also, please see the previous comment by mbone for more elaboration--
Mmm. (Score:2, Interesting)
I've tried the USGS, the IAU, and a general google search. This is going to annoy me to no end until I get an answer.
Re:Mmm. (Score:5, Informative)
I believe that Dactyl, the moon of the asteroid Ida, is only about 100 meters across.
The exception occurs in planetary rings, where a moon has to be bigger than the ordinary rubble of the ring to be considered a moon.
Parent
Re:Rubble,rubble (Score:2)
Saturn has at least five "Shepard Moons" - S15 bounds the outer edge of the A ring, S13 and S14 dance with the F ring, giving it a braided appearance, and S10 and S11 lie just outside the ring system.
Jupiter also has a ring satellite, J9, as does Neptune, Galatea, and I suspect that Uranus has some undiscovered ones also.
All of these satellites are small, and most if not all were discovered by the Voyager spacecraft.
More fun ring images and facts can be found on the ringmaster [nasa.gov] web site.
Well, it's not the size, (Score:2)
Must be a slow news day :) (Score:2, Funny)
This just in . . . (Score:3, Funny)
Scientists are now beginning the process of officially naming the two new worlds. This is expected to pass through several committees before signature in March 2007.
With the discovery, Jupiter is now 3,845,108,491 moons ahead of closest rival Saturn in the race for biggest posse in the solar system.
Moons orbital data chart (Score:2, Informative)
Planetary Satellite Mean Orbital Parameters [nasa.gov]
What's the cutoff? (Score:2)
3 km, Eh? Almost Able To Resolve... (Score:2)
Re:Would be fun to live on jupiter.... (Score:2)
Re:Would be fun to live on jupiter.... (Score:2)
The surface gravity on Jupiter can be calculated from Newton 's Law of Universal Gravitation:
F = G * (mass of Jupiter) * (your mass) / (radius of Jupiter squared)
The ratio of the force of gravity on Earth to that of Jupiter is thus:
Mass of Jupiter / Radius of Jupiter squared
Jupiter has a mass that is 318 times that of the Earth and a radius that is 11.2 times that of the Earth.
The surface gravity would be 318/(11.2)(11.2) = 2.5 times the Earth's.
Now I have pulled 3 G's before -- and I am thicker than a few centimeters, although some still call me a pile of goo.
Re:Would be fun to live on jupiter.... (Score:2)
So your value is 2.3 instead of 2.5.
Perhaps the difference is from using different values for the radius of a gas giant.
Re:moon (Score:2)
I'd consider it space junk. But then again, I guess it holds some value for some scientists.
Re:I thought it only had 16 moons (Score:3, Interesting)
As for where the other satellites came from....
The discovery of the last eleven of them is discussed here [space.com] (39);
the eleven before those are discussed here [hawaii.edu] (28);
the one before those is discussed here [space.com] (17);
Re:moon (Score:4, Informative)
Parent
Re:I claim this new planet in the name of Slashdot (Score:2)
Question: What would the planets be named... (Score:2)
Re:I have to ask (Score:2, Funny)