Neptune Trojans not confined to ecliptic plane

[mikeemmert]

I was reading the morning Yahoo! News when I came upon this interesting article. The Sun/Neptune Lagrange points L4 and L5 are located about 60 degrees ahead of Neptune in it's orbit around the Sun, and 60 degrees behind; the mathematical solution that Lagrange came up with actually shows that the Sun, Neptune, and the Lagrange points form equilateral triangles and the points are very slightly outside of Neptune's orbit.<br /><br />An object slightly off the Lagrange point will slowly orbit the Lagrange point in about 10,000 years. This is an elongated, tadpole-shaped orbit. Such objects are called "Trojans"; Jupiter has a huge swarm of them. <br /><br />Three Neptune Trojans were already known. A fourth one was discovered, but it had an inclination to the ecliptic plane of 25 degrees.<br /><br />The survey that found it was designed to look in the ecliptic plane, so the discovery of the fourth object was unlikely. The fact that it <i>was</i> discovered indicates that there are a lot more of them. This tends to confirm some GravitySimulations that I have done in which such objects pass up and down through the Lagrange points and drift slowly back and forth with respect to Neptune.<br /><br />The discovery of this object bolsters a suspicion I have had since doing my series of simulations of this scenario. That started with the idea that Xena (2003 UB313) is the lost moon of Triton, Neptune's enigmatic backwards orbiting moon. That suspicion is that the orbital plane of the Xena/Triton binary was <i>perpendicular</i> to the plane of the ecliptic. It makes the capture of Triton by Neptune much easier.<br /><br />If such a pair had such an orbit within the Lagrange zone, then it would preferentially eject other material in the Lagrange points into highly inclined orbits around the Sun.<br /><br />I am eagerly awaiting the completion of

 

[jmilsom]

I just read the same article on Yahoo and I instatntly thought of you and was going to bump your "2003 UB 313 is the lost moon of Triton" thread! I do think your theory has credibility. But what do you think about Trujillo stating <i>The Neptune Trojans are a thick 'swarm,' not a thin population confined to the plane</i>? Is there enough evidence to support this. I agree there must be a lot more of them, but a thick swarm? <div class="Discussion_UserSignature"> </div>

 

[vogon13]

Jupiter has Trojans in orbits exceeding 20 degrees in inclination.<br /><br />Jupiter also seems to have more Trojans inclined 5 to 10 degrees than 0 to 5 degrees.<br /><br /><br />So I am not sure this Neptune discovery is some 'big deal'.<br /><br />BTDT.<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>

 

[alokmohan]

It means we are going to have third belt of asteroids.

 

[mikeemmert]

Well, if by "thick swarm" he means spatial density, well if you add large inclinations then the volume of space increases drastically. So, no, the swarm I don't think is "thick".<blockquote><font class="small">In reply to:</font><hr /><p>I agree there must be a lot more of them<p><hr /></p></p></blockquote>Indeed. See vogon13's post.<br /><br />Vogon: thanks for the data points. This is much appreciated. It is another piece of evidence that the Lagrange points extend outside of the plane of the ecliptic.

 

[dragon04]

This is sort of off topic, but you seem to be a "go to" guy on orbital mechanics. I have a question or two, and I'll try to ask it in a way you'll understand regarding Lagrange points.<br /><br />I know what they are. Let's frame this to Neptune's L4 point.<br /><br />How much does that L4 "oscillate" due to gravitational influences of planets more Sunward? Or are the Sunward planets even a significant influence?<br /><br />Uranus, Saturn and Jupiter in particular (the latter two being far more massive) orbit the Sun more rapidly.<br /><br />In addition, relative to Neptune, their orbits are "elliptically" different as is their relative inclanation/declination with respect to Neptune's orbit around the Sun.<br /><br />So if you graphed the "drift" of Neptune's L4 point, would each of the above named objects be indicated at their closest approach to that point?<br /><br />Finally, would it be fair to say that given the makeup of the solar system that Earth's L4 point would be more "stable" than say, Jupiter's due to the gravitational influences of the larger planets with respect to the inverse square law nature of gravity?<br /><br /><br /><br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[mikeemmert]

<blockquote><font class="small">In reply to:</font><hr /><p>This is sort of off topic, but you seem to be a "go to" guy on orbital mechanics.<p><hr /></p></p></blockquote>Gee, thanks, that's flattering, but I would consider the Go To guy to be Tony Dunn. I'll edit a link to him after I finish this post.<blockquote><font class="small">In reply to:</font><hr /><p>How much does that L4 "oscillate" due to gravitational influences of planets more Sunward? Or are the Sunward planets even a significant influence?<p><hr /></p></p></blockquote>This is a pretty complex question. Strangely, Neptune seems to have more influence on a Neptunian Lagrangian than the inner planets do, despite their higher mass (for the gas giants). What's actually going on here is that the Sun's influence is overwhelming.<br /><br />The fact that Neptune's orbit is not quite circular imposes a spiral on the main drift. So you have the object making a large, slow oscillation with respect to Neptune's average position and a tight spiral imposed on the main drift.<br /><br />What's happening here is that planets interior to, or exterior to, the Lagrange system change the center of mass of the <i>entire solar system</i>. If you have GravitySimulator, you can see the effect by watching the monitors and noting the change in the distance from the Sun to either the Lagrangian or Neptune. It's a little hard to see on the monitor. I don't know if that's an artifact. You'll have to ask Tony. He's pretty honest about artifacts, yeah, there are observational artifacts everywhere, and computational ones, too. We do the best we can and get pretty good results anyway, I think (or hope). Try http://www.orbitsimulator.com/gravity/articles/what.html<br /><br />http://uplink.space.com/showprofile...&page=&view=&sb=&o=&fpart=1&v</safety_wrapper

 

[tony873004]

For those who have Gravity Simulator, here's a simulation of Neptune's trojan asteroids. Starting conditions courtesy of JPL.<br /><br />http://orbitsimulator.com/gravity/simulations/NeptuneTrojans.gsim<br /><br />And a screen shot:<br />http://orbitsimulator.com/gravity/Ntrojans.GIF

 

[3488]

There is a chance that New Horizons could encounter a Neptune Trojan as the spacecraft will be passing through the region where the trailing Neptune trojans are. Will be interesting to compare any of these with the Saturn moon Phoebe. Fascinating possibily. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[mikeemmert]

Hi, Dragon04;<br /><br />I would like to comment on Tony's image of Neptune's Trojans. The spiral I mentioned can look looser on the screen if the object's eccentricity is greater than 0. An inclined object also <i>appears</i> to have a looser spiral, but that is a perspective effect. Please forgive my representation; I was thinking of simulations I did where the objects had eccentricity of 0 and very low inclinations (like 0, for instance). In those cases, the spiral looks tighter.<br /><br />What I was doing was assuming that you were trying to determine the effect of other objects on the stability of the Lagrange zones, so I fogot about eccentricity and inclination, which actually I shouldn't do. I have done eccentric and inclined orbits.<br /><br />Relatively small masses in the other Lagrange point (than the one you are looking at) have more of an effect than you might think. But that doesn't seem to explain how the Lagrangians get loose from the stability zones.<br /><br />A paper I read somewhere seems to give the best explanation, although I haven't simulated it yet since it requires special tactics that I have thought of but haven't worked out in enough detail. Once an object gets out of the Lagrange stability zone, it will encounter Neptune. These encounters increase the objects energy with respect to Neptune and the Lagrange points. Collisions can impart this energy to the Lagrange zones, especially if the Lagrangians have not yet finished accreting.<br /><br />Simulating this could probably best be done by making the Lagrange objects very large without increasing their masses (think of giant soap bubbles). This simulates the increase in surface area, and thus the increase in probablility of collision, that you get from the square-cube law. (The total area of the asteroid belt is much larger than the total area of the Earth. Dust discs are much more visible at stellar distances than planets in spite of their lower mass. Same principle applies).<br /><b></b>