2003 UB 313 is the lost moon of Triton

[mikeemmert]

I have, since the initial post in this thread, simulated a number of flybys of binaries by Neptune. Patterns are beginning to sort themselves out. There are several poosible results of a flyby. The binary can remain intact if the velocity is too high, corresponding to a high inclination of the binaries' orbit around the Sun with respect to Neptune's, or a high eccentricity or having the wrong angle with respect to Neptune. The binary can separate without a capture. One object can be captured and the other flung out at a higher velocity, as I believe happened to Triton/Xena.<br /><br />A fourth possiblity is that the binary objects can collide. The collision itself is beyond the scope of my computer's programming, but work by others regarding such a collision of a Lagrange object with Earth indicates that the cores of the objects can merge and the mantles can form another object.<br /><br />With the parameters I was using (1.3 km/sec velocity approaching from 120,000,000 km away from Neptune, 20,000 km distance between the binary objects, 310,000 -560,000 km approach distance with speeds at closest approach of around 7 km/sec), the objects collided right about at 1000 meters per second, about the speed of a rifle bullet.<br /><br />I think such a collision resulted in a second pair of objects; Pluto and 2003 EL61 "Santa":<br /><br />http://64.233.167.104/search?q=cache:-Is9XpqwZXEJ:www.gps.caltech.edu/~mbrown/2003EL61/rabinowitz.pdf%202003%20EL61%20Arizona&hl=en<br /><br />Santa is a strange object whose discovery was announced at the end of July. The most striking feature of it is it's high density, about 3000 kg/cubic meter. This is in a region of icy bodies with low densities. Another strange characteristic of this thing is it's extremely rapid rate of spin. It's day is only 3.9 hours long.<br /><br></br>

 

[serak_the_preparer]

Well, whatever it is, it is sort of interesting:<br /><br />Tenth planet as bright as fresh snow by Maggie McKee (New Scientist)<br /><br />11 April 2006<br /><br /><i>. . . The fact that Xena is smaller than initially thought means it must reflect about 86% of the light that falls on it - making it about as bright as fresh snow and brighter than every other solar system body except Saturn's moon Enceladus. Spectral observations suggest its surface is covered with frozen methane, like Pluto. <br /><br />But unlike Pluto, which is mottled by both bright and dark splotches, Xena is so uniformly bright that it is impossible to tell how fast it is rotating. "When we made the size measurement, we were thoroughly shocked," Brown told New Scientist. "Such a high albedo is simply unprecedented other than the very odd Enceladus."<br /><br />Richard Binzel, a planetary scientist at the Massachusetts Institute of Technology in Cambridge, US, agrees. "Space is a dirty place," he says, explaining that particles from the solar wind alter the structure of ices, darkening them over time. "It's very hard to keep a surface bright and white - it requires some process to keep the surface fresh..."</i>

 

[mikeemmert]

Howdy, Serak;<blockquote><font class="small">In reply to:</font><hr /><p>... unlike Pluto, which is mottled by both bright and dark splotches, Xena is so uniformly bright that it is impossible to tell how fast it is rotating.<p><hr /></p></p></blockquote>There is another possible explanation for why Xena's brightness doesn't change with time. It could be that it's rotational axis is pointing towards the Earth. In that case you would not see any brightness variations.<blockquote><font class="small">In reply to:</font><hr /><p>"Space is a dirty place," he (Richard Binzel) says, explaining that particles from the solar wind alter the structure of ices, darkening them over time. "It's very hard to keep a surface bright and white - it requires some process to keep the surface fresh..." <p><hr /></p></p></blockquote>It's kind of hard to imagine some energy source for creating a continuous supply of methane vapor to keep the surface fresh. There's unlikely to be a significant supply of radioactive elements to keep Xena's core warm. Xena has a moon but it seems to be rather small, so tidal heating seems to be out. (I know from previous posts that there are those who disagree with this and they are welcome to post.)<br /><br />But, with the unmistakeable spectrum of methane on Xena's surface, it's hard to imagine that it's not sunburned, a little.<br /><br />There are still the radiometric measurements of Xena's size to consider. Hubble observations do not cause those to cease to exist.<br /><br />Of course, if there was a heat source aside from solar energy, This would mess up the radiometric measurements and then Xena would be smaller than that technique would measure.<br /><br />I would definitely like to see a third opinion from the Spitzer Space Telescope. The last time they tried to get these measurements, they literally missed. The wrong data got put into the machine and there was a pointing error.<br /><br />I have predicted that Xena would have a mass within 15% of that of Triton. I would