Jupiter's "Mini-Me" Solar System Grows

An anonymous reader writes "University of Hawaii's robotic telescopes have discovered 8 new moons for Jupiter, thus bringing its mini solar system to 48 total. No one knows how Jupiter dissipates the energy of these likely asteroid captures, unless it once had a massively larger atmosphere. Indeed, its ion cloud today seems to spell doom for what Sir Arthur C. Clarke indicated, is another reason to avoid probing life on Europa. ('All these worlds are yours--except Europa. Attempt no landings there.'-- 2010: Odyssey Two). As an aside, one of those NASA sites seem technically to be doing text-to-speech in a very familiar-sounding, Stephen Hawkings version [MP3] of those articles."

Comments

Bad text to speech....

[BWJones]

Geez, I checked out that text to speech link and was surprised the voice was not of any higher quality. Mac users at least, have had much better text to speech quality for years now going back to the mid 90's.

Size?

[Anonymous Coward]

What makes a satellite an acceptable .. satellite? Obviously there's a size issue but is there something else that makes a particular body labeled as a satellite (In the 'moon' sense)?

What is a moon?

[$$$$$exyGal]

Specifically, my question is:

How close does an natural astronomical body have to orbit a planet for it to be a moon?

I know there has been much debate about what a planet is (the Pluto debate, etc), but what exactly is a moon? Would it be possible for an object to travel into the Solar System, and then whip around Jupiter, and then reenter the Solar System, etc (without actually getting that close to the sun). If it did that, then would it be a Jupiter-moon?

Re:What is a moon?

[Guppy06]

"How close does an natural astronomical body have to orbit a planet for it to be a moon?"

Close enough that it orbits the planet and not the system star. The sun is so much bigger than all the other planets (combined, even) that there is a definite line between those two.

"(the Pluto debate, etc)"

IMO, Pluto qualifies as a planet because it's held together by its own gravitational forces. Planetoids are held together solely by chemical forces (ie. just one big rock). Heck, Pluto even has its own atmosphere.

"but what exactly is a moon?"

Pluto and Charon confuse things a little bit in this reguard because it can almost be called a binary planet.

"Would it be possible for an object to travel into the Solar System, and then whip around Jupiter, and then reenter the Solar System, etc (without actually getting that close to the sun)."

No, because the sun is massive compared to Jupiter, like 1000 times more massive. An object would have to get extremely close to Jupiter (astronomically speaking) for it to notice Jupiter's pull more than the sun's. Note that all the other outer planets still orbit the sun, even though Jupiter is often much closer to each of them. Jupiter affects the orbit of these planets slightly, but those orbits are still around the sun.

Re:What is a moon?

[CheshireCatCO]

There *is* a natural limit to how far out you can get and still be orbiting a planet, like Jupiter. That limit (roughly) is the Hill radius*, which goes like (m/3 M)^(1/3) a, where m is the mass of the planet, M is the mass of the Sun, a is the planet's orbital semi-major axis and 3 is 3. For Jupiter, this is about half of an astronomical unit. That's actually a pretty big sphere of influence, since Jupiter is only 5.2 AU from the Sun to start with.

There are some who would call objects in the same helicentric orbit as the planet "moons". This class of objects includes the Trojan asteroids of Jupiter, as well as Earth's "second" moon. On the whole, however, astronomers seem to prefer to only consider something a moon if it really orbits the planet.

* It's actually a eeensy bit more interesting than that. Prograde moons can't seem to orbit stably much further than half of a Hill radius from their planet, while retrograde moons can orbit up to about a full Hill radius.

Picture of Jupiter

[rodney dill]

The astronomy picture of the day a few days ago had a nice moving picture of Jupiter with two moons. Where did the other 46 go?


(feeble Karma saving attempt)

Re:Europa's not the only possibility

[Anonvmous Coward]

"Life would be underwater, in an ocean tens of kilometers deep, the radiations won't penetrate that far. So don't rule out Europa."

Just wanted to bring up a point that's not considered very often: Life here on Earth exists in some VERY harsh environments. I don't think there's a natural area of Earth that's completely devoid of life. If you go underwater deep enough, you'll find life forms that exist without any light reaching them near some very hot thermal vents in the ocean floor.

Frankly, I'd be surprised if an ocean bearing planet or moon didn't have life.

Re:I can only see 3 moons though...

[saskboy]

Sorry, on second though, I think it was a 6" Newtonian telescope with a R.A. auto tracking motor. It was possibly a 12mm eyepiece, and the camera is a Canon Powershot S30 with 3X zoom and held against the eyepiece as steady as I could.

I wonder how my post could be construed as "flaimbait"? Slightly offtopic, I conceed, but people interested in Jupiter news might like to see how it looked just last Thursday. You never know when it will just pack up and leave with all it's moons in tow.

Recent Moon Additions

[FosterSJC]

For those interested, here are the slashdot threads for the last two moon additions to Jupiter:

1. New Moon of Jupiter Discovered

S/2002 J1- Catchy name, eh? Beats the hell out of say, Europa or Ganymede. Incidentally, this ran on 12/28/02.

2. Jupiter's 11 New Moons

This one ran on 5/17/02.

Re:Recent Moon Additions

[CheshireCatCO]

"S/2002 J1- Catchy name, eh? Beats the hell out of say, Europa or Ganymede."

That won't be its permanent name. All bodies are given temporary names of that kind until the Internation Astronomer's Union confirms their permanent names. Besides some slight beaurcratic overhead intended to keep astronomical nomenclature standardized, this is also because they want to be sure it's really a new object.

Exactly !

[Evil Pete]

How is a radiation field going to penetrate kilometres of ice ... or even a few metres ? It can't. Timothy didn't even bother to read the original article which made NO mention of that conclusion .. he thought that up by himself.

Europa still looks good. In fact it looks like the best place to me.

Re:Europa's not the only possibility

[RayBender]

This is a bit of a repeat story, so the response is worth repeating: high levels of radiation do not preclude life, and in any case the idea was that Europan life would be under kilometers of ocean.

It's amazing how much radiation certain bacteria can survive, though..

By the way, NASA is thinking about a new mission to the Galilean moons, called JIMO . Very exciting stuff - it's amazing how much more you can do with a nuclear propulsion stage.

ion cloud is irrelevant

[g4dget]

Any life on Europe is likely going to be miles deep under water. An ion cloud and radiation hitting the surface is not going to make any difference there. So, the chances for Europan life are as good or as slim as they have ever been. However, the radiation may make exploration more difficult.

Re:But what are their names?

[CheshireCatCO]

Jupiter's moons are all named (saith the official Internation Astronomers' Union rules) after paramours of Jupiter/Zeus. There are a few exceptions, named for the nurses of the young Jupiter.

But even with Zeus's ... er... excesses, we're running out of names.

(Saturn's moons are all titans, I believe, Neptune's are minor gods and goddess associated with, well, Neptune, and Uranus's are named for Shakespeare and Pope characters. Mostly sprites, I think.)

Re:Spell doom for the system

[wideBlueSkies]

Yeah, but they're working on this technology using the work done at Lake Vostok as an example.

Re:Spell doom for the system

[C21]

I see it as launching a craft that would put into orbit around europa and detach mini probes that would plunge/melt through the surface, transmitting discoveries to the "mother ship" and thus back to earth. All very "simple", electromagnetic waves can go through water, you know...

Re:Spell doom for the system

[passion]

All this, while not contaminating any alien species' primordial goop, and wiping them all out just as we discover them.