New capture scenario - Triton

[drwayne]

Neptune's large moon Triton may have abandoned an earlier partner to arrive in its unusual orbit around Neptune. Triton is unique among all the large moons in the solar system because it orbits Neptune in a direction opposite to the planet's rotation (a "retrograde" orbit). It is unlikely to have formed in this configuration and was probably captured from elsewhere. <br /><br />Rest of the story:<br /><br />http://www.physorg.com/news66489496.html <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[vogon13]

This is the yon wee beastie of which you post:<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>

 

[doubletruncation]

<blockquote><font class="small">In reply to:</font><hr /><p>I don't agree that this is a "new" capture scenario. It is a three body problem variation usually known as sphere of influence capture. It might have been a new idea in Newton's Principia however.<p><hr /></p></p></blockquote><br /><br />I agree with this. I feel like people mention three body interactions as solutions to problems like these pretty often, and I'd be surprised if no one has ever thought of it as a possible origin for Triton before. <div class="Discussion_UserSignature"> </div>

 

[tony873004]

Isn't this what Mikeemmert, member of this forum, has been speculating for some time?

 

[mikeemmert]

Indeed that was me: <br /><br />http://uplink.space.com/showflat.php?Cat=&Board=sciastro&Number=297646&fpart=1&PHPSESSID=<br /><br />Glad to see there's at least one person who doesn't think I'm nutz.<br /><br />Now, I have specifically named Xena (2003 UB313) as the binary partner. That's my story and I'm sticking to it. The reason is that when Triton was captured, the energy lost in it slowing down was absorbed by the binary partner, propelling it into a higher orbit. Xena's <i>waaaaayyy</i> out there, the mark of a three-body interaction.<br /><br />In case anybody missed any earlier posts, I think the Triton/Xena binary formed in a Sun/Neptune L4 or L5 point. Of course, there are <i>two</i> stable Lagrange points and if objects form in one, similar objects should form in the other. And I think that in the other corner, weighing in at the same mass as Triton/Xena, was Pluto/Santa.<br /><br />I'd like to thank Tony Dunn for turning me on to GravitySimulator. When I simulated flybys of Triton/Xena past Neptune, I noticed that in several encounters, the two objects collided!<br /><br />This would explain bizzarre 2003 EL61's rapid spin, elongated shape, and high density. It also apparently lost a lot of mass, nearly all of it's ice and a good deal of rock as well.<br /><br />All four objects, Triton, Xena, Pluto, and Santa I think once had the same mass, which was about the mass of Pluto. Triton, once in orbit around Neptune, inevitably ate Neptune's original moons and got fat. Santa went into a frantic spin and lost weight. Xena probably avoided further collision in it's isolated location, Gabrielle having been formed from debris liberated by tidal forces as Neptune, Triton, and Xena interacted.<br /><br />This has been a very fun project. It's good to see some measure of confirmation.

 

[robnissen]

You should think about more formally running your gravity simulations. There might be an excellent paper in there somewhere.

 

[brandbll]

Santa? gabrielle? What is going on here? Are these theoretical planets or moons? <div class="Discussion_UserSignature"> <p><font size="3">You wanna talk some jive? I'll talk some jive. I'll talk some jive like you've never heard!</font></p> </div>

 

[mikeemmert]

I was working on it, but when Hubble measured Xena's size and it turned out to be Pluto's size, I realized that my models needed some upgrading. When I started that, I realized I needed a little bit more systematic approach. I have a job now, too, with the Census Bureau. But today I have taken some time for this.<br /><br />Time, time...for example I don't have time to properly research this post. I'm going from memory below. It's pretty much a political issue anyway.<br /><br />This kind of brings to mind the little tussel between Dr. Ortiz from Spain and Mike Brown at Caltech. Mike Brown had discovered 2003 EL61, "Santa", the wierd cigar-shaped object in the Kuiper belt. But he kept it under wraps because there was a lot to learn about the object.<br /><br />Meanwhile, Dr. Ortiz independently discovered the object. One of the first things he did was to try to see if anybody else had photographed it. That's called, "precovery" and helps pin down the object's orbit. He apparently found out about Mike Brown's discovery. He was accused of "hacking in to" Brown's website. Ortiz accused Brown of sitting on the discovery.<br /><br />Brown publicly wondered if Ortiz had "stolen" his discovery. I firmly believe Ortiz & Co. discovered it independently. If he hadn't, he wouldn't have known to search for it. "Gimme a clue..."<br /><br />Space.com has now done an article on the Triton capture scenario. It's accompanied by an illustration, which clearly shows the Triton companion as being significantly smaller than Triton (it's in the foreground in front of Triton, so you know it <i>is</i> depicted as smaller.) I think they were of equal size. Just a couple of months ago I said firmly that I thought Xena and Triton would be the same size & had a fine meal about it (see below). Now the model has changed.<br /><br />That's science for you...<br /><br />I need to download the latest version of Photoshop, which I can now do thanks to the Census Bureau. But I have to

 

[silylene old]

I immediately thought of mikeemmert's thoughts and discussions when i read the triton piece too.<br /><br />Good work, Mike ! <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[mikeemmert]

Thank you, silylene.<br /><br />The University of California at Santa Cruz press release, which I believe is linked above, noted that Dr. Agnor was going to model other possible capture scenarios. I think Titan is a Lagrangian, so I looked at the Saturn system on Wikipedia so see if there is any possible scenario, and this time I decided to jump the gun a little.<br /><br />If you look at the masses of Saturn's moons (see "Wikipedia - Saturn", they have a nice table there), you will see that Tethys, Dione, Rhea, and Iapetus have similar masses. I was thinking that perhaps Iapetus, with it's very far out orbit, might have been flung out to slow Titan down. So I modeled it.<br /><br />I copied Mimas, Enceladus, Tethys, Dione, and Rhea by copying their orbits and masses onto Gravity Simulator, along with the mass given for Saturn with it being the central object. Iapetus, however, was given a circular orbit with an altitude of 739,000 kilometers, as if it were a Galilean moon. At this point, the Saturn system looked like a smaller version of the Jupiter system, having four large moons plus debris (Mimas and Enceladus).<br /><br />I then put Titan on a very eccentric orbit which receded out to almost 40,000,000 kilometers and came in about 750,000 kilometers on closest approach. Although this put Titan below escape velocity, it did allow me to put the machine on "don't plot" and go off and read Yahoo! News and Uplink forum. I checked back every few minutes.<br /><br />What I was doing here was a preliminary simulation, just to see what happened. I was looking for changes in Iapetus' orbit. After 162 simulated years, Iapetus had assumed an elliptical orbit of about 730,000 x 930,000 km. So far, so good. I was thinking that a really close encounter with Titan would fling Iapetus out to a pretty far distance.<br /><br />Instead, Titan ate Iapetus! I didn't see the event because I was reading about Ahamdi-Najad's letter in Free Space. But I could tell because I had given

 

[silylene old]

Mike, please keep up the simulations. I for one find them to be very interesting.<br /><br />If you could start a thread on this one topic, and post in some of the more interesting diagrams of orbital interactions or collisions, I would be interested.<br /><br />I am particularly interested in if you can find any chances for slow motion collisions. By this, I mean two moons which collide with a delta-v that is minimal Perhaps a delta-v of just a few tens of km/hr or less?). I think that the two moons would need to be nearly co-orbital for this to happen (not orbiting each other, but rather sharing almost the same orbit around the planet). As you know, Saturn has currently three pairs of nearly co-orbital moonlets. Is there any way to perturb these into a slow motion collision?<br /><br />(I have wondered if Iapetus could be the result of a slow motion collision) <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>