Can moons have their own moons?

[hal9891]

So can moon revolving around planet have it's own moon? Could such system at least theoreticaly form, if so why there are none of them in solar system? <div class="Discussion_UserSignature"> <div style="text-align:center"><font style="color:#808080" color="#999999"><font size="1">"I predict that within 100 years computers will be twice as powerful, 10000 times larger, and so expensive that only the five richest kings of Europe will own them"</font></font><br /></div> </div>

 

[MeteorWayne]

It would be a very unstable configuration. When the moon's moon was on the same side as the planet, it's orbit would be shifted. When the moon's moon was on the other side, the planet would be shifted.<br />In the end, the moon's moon would likely be ejected from the moon's sytem, to spiral into the planet, impact the moon, or be ejected into solar orbit, where it would hit a planet, spiral into the sun, or be ejected from the solar system....etc <img src="/images/icons/smile.gif" /><br /><br />It is not impossible, but the orbit of the moon's moon would have to be perfect, within a micron per second, and a millimeter in position.<br /><br />Very low odds <img src="/images/icons/smile.gif" /><br /><br />MW <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[SpeedFreek]

So why is the same not true when considering planets orbiting a star having moons? I.e. when the moon of a planet was on the same side as the star, why isn't it shifted? Or is it? <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[MeteorWayne]

The same is true, but the distances are usually much greater, and since distance is the major factor in the gravity equation (F= (mass difference) X (distance between squared) despite the greater mass of the star, the distance between the star and planet/moon reduces the effect. <br /><br />F = G Ma Mb / r2<br /><br />Ma and Mb are the masses of the two objects you are considering, r= the distance between them<br /><br /><br /><br />I didn't say that very well, I'll try and rephrase if nobody bails me out <img src="/images/icons/smile.gif" /> <br /><br />Edit add link: Fig(uring) Newton <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[SpeedFreek]

Thanks for that MeteorWayne <img src="/images/icons/smile.gif" /><br /><br />How likely is it that an outer planet of a solar system, distant from its star, could have a moon in a distant orbit around it, with a small satellite around that moon?<br /><br />Do the chances of a moon having a moon increase with the distance of the planet from the star, and the distance of the moon from the planet? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[MeteorWayne]

As I understand it, the likelyhood increases the further a planet is from the star, and how far that planet is away from another massive planet.<br /><br />If a planet is far enough out, and if the planet spacing leaves it gravitationally isolated, then the distance of the mother moon from the planet is not as important. The specific circumstances would be critical. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[hal9891]

But if moon orbits planet in great distance and moon orbits moon in very close distance would that help much? <div class="Discussion_UserSignature"> <div style="text-align:center"><font style="color:#808080" color="#999999"><font size="1">"I predict that within 100 years computers will be twice as powerful, 10000 times larger, and so expensive that only the five richest kings of Europe will own them"</font></font><br /></div> </div>

 

[willpittenger]

In the strictest sense of the phrase, our Moon did have its own "moons" -- man-made ones. However, as MeteorWayne noted, their orbits were unstable. Apollo 10's orbit shift considerably. They wanted to have Snoopy simulate the exact same approach that Apollo 11 would make. However, because the orbit shifted, they missed. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

I should note that no planet closer than Earth to our Sun has a moon. All known moons in our solar system orbit a planet that is at least 1 AU out. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[MeteorWayne]

If I understand your question, the answer is maybe. It depends on a lot of things being near perfect. If not, pfoot, the moonlet will go away somehere.<br />Being far from the planet is only useful if the planet is far from the star, and far from any other planet. If not, the moonlet will be ejected to somewhere else. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vogon13]

Objects in 1:1 resonance are known, Cruithne, Pandora, etc.<br /><br />Pandora meets to a degree your criteria.<br /><br />It may be possible the craters Valhalla and Asgard on Callisto might have been formed from co-orbitals (possibily additionally orbiting each other) that Callisto zorched.<br /><br />Hyperion may be a tidally evolved (escaped) satellite of Titan.<br /><br />The 'outie' asteroidal satellites of Jupiter (and possibly the other gas giants) are expect to be 'enmooned' in a similar percantage to the parent population of Jupiter Trojans.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[why06]

I've got a question that may or may not complicate things, anyway Im pretty sure they do, but just for the sake of confirmation:<br /><br />Do moons have to orbit planets?<br />-how about other large bodies?<br /> <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[brellis]

Post deleted by brellis <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>The trojans trailing the outer-planet moons are in a relationship with those moons. Almost moon-of-moon...<p><hr /></p></p></blockquote><br />???? The trojans I know of orbit the Sun -- not Jupiter or Saturn. Hence, they could be "almost moons", but not "almost moons of moons." <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[brellis]

Post deleted by brellis <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>This chart illustrates how slim the chances are of a small trojan getting captured via Jupiter into an orbit around one of its moons.<p><hr /></p></p></blockquote><br />Not really. Jupiter's system is rendered too small to be useful in that regard. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[qso1]

Excellent question HAL9891.<br /><br />Actually, one planet has moons orbiting its own moon. Earth has at least one that I can think of. Clementine, artificial satellite in orbit around the moon. But its too small to have a noticeable effect on earth.<br /><br />MeteorWayne has described the problems that would occur in such a system quite well. But just imagine if we find extrasolar worlds with moons orbited by submoons if you will. A whole new class of object would be categorized. I like the originality of this idea as I don't think I have ever seen serious consideration of it before.<br /><br />I have an idea for another bizarre class of object which I will post soon. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[hal9891]

Thanks qso1!<br /> And I've got another question: could there exist two gas giant planets orbiting each other while both orbiting star kinda like Pluto-Charon system? <div class="Discussion_UserSignature"> <div style="text-align:center"><font style="color:#808080" color="#999999"><font size="1">"I predict that within 100 years computers will be twice as powerful, 10000 times larger, and so expensive that only the five richest kings of Europe will own them"</font></font><br /></div> </div>

 

[mithridates]

What about some of the really distant moons of Jupiter? The most remote one is 30 million km out and has an orbital period of over 900 days. Shouldn't a moon like that be able to have its own moon? <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[vogon13]

Hello? Hello?<br /><br />{thumping computer screen}<br /><br />Is this thing working ??<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[mithridates]

何ãŒä½•ãŸã©ï¼Ÿè¨€è‘‰ãŒé€šã˜ã¦ãªã„よã†ãªæ°—ãŒã™ã‚‹ã¨ï¼Ÿ<br /><br /><br /><img src="/images/icons/wink.gif" /> <br /><br />(Just joking. I missed what you said up there. It was 2:30 am. *Shrug*) <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[qso1]

HAL9891:<br />could there exist two gas giant planets orbiting each other while both orbiting star kinda like Pluto-Charon system?<br /><br />Me:<br />Keep in mind I'm not a professional astronomer but I don't really see why such a thing wouldn't be possible albiet probably rare. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[qso1]

mithridates:<br />What about some of the really distant moons of Jupiter? The most remote one is 30 million km out and has an orbital period of over 900 days. Shouldn't a moon like that be able to have its own moon?<br /><br />Me:<br />See previous post. And to that I would add one of the things we may yet discover in our system is a moon similar to Phobos or Deimos but with a tiny (Several hundred feet diam.) moon orbiting it as it orbits a planet like Jupiter or one of the other gas giants. The further a moon is from a large planet, the better the chance it could have its own moon.<br /><br />A system not unlike the asteroid 243 Ida and its moon Dactyl. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[willpittenger]

Would dust count as a "moon?" I figure some orbits some of the moons in this system. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[MeteorWayne]

Not unless you consider the billions of billions of submillimeter meteoroids that hit the earth every year planets. After all, they orbit the sun. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>