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View Full Version : Is Neptune's moon Triton a captured Kuiper Belt Object?



SolarSystemGeologist
2007-Nov-10, 02:28 AM
I read somewhere that astronomers think it's possible, since it circles Neptune backwards, and has a similar composition to Pluto.

Noclevername
2007-Nov-10, 02:47 AM
It's entirely possible.

laurele
2007-Nov-10, 06:18 AM
I read somewhere that astronomers think it's possible, since it circles Neptune backwards, and has a similar composition to Pluto.

I've heard this theory and also the one that Triton was once a full fledged planet orbiting the sun that somehow got captured by Neptune. Conversely, I've also heard the theory that Pluto is a former moon of Neptune that somehow got away though in recent years this idea has received less credence (not sure why).

tony873004
2007-Nov-10, 06:26 AM
I've heard this theory and also the one that Triton was once a full fledged planet orbiting the sun that somehow got captured by Neptune. Conversely, I've also heard the theory that Pluto is a former moon of Neptune that somehow got away though in recent years this idea has received less credence (not sure why).

Pluto is in resonance with Neptune. There would need to be some mechanism that delivered it to the resonance after its escape. It's more likely that Pluto was captured from a solar orbit into resonance by Neptune when it migrated early in its history. Pluto also has 3 moons. We know of no example where a moon has moons of its own.

There's a theory that Triton was part of a binary system that passed close to Neptune. The binary was split, with one member escaping and the other member (Triton) entering a stable orbit around Neptune.

SolarSystemGeologist
2007-Nov-12, 05:52 AM
We know of no example where a moon has moons of its own.Do you think it's possible there are moons in other solar systems that do have moons of their own?

Ronald Brak
2007-Nov-12, 07:10 AM
I don't think there are any moons that are really in a position to have moons of their own, at least not for long. If you try to orbit someting around a moon it has a habit of eventually smacking into it as moon moon orbits are unstable over time as they become more and more eccentric.

EDIT: Sorry, I missed the bit about other solar systems. I don't see any reason why not, there are situations where it would be stable for a long, long time, but as tony says below, probably rare.

tony873004
2007-Nov-12, 07:56 AM
Do you think it's possible there are moons in other solar systems that do have moons of their own?

I wouldn't want to say it can never happen. The exosystems we're finding always surprise us. But because of the dynamics involved, I'd guess its pretty rare.

Sticks
2007-Nov-12, 09:34 AM
But if you had a planet A being orbited by moon B, would not a further moonlet orbiting C have the possibility of orbiting planet A as well in a figure of 8 pattern?

grant hutchison
2007-Nov-12, 01:28 PM
But if you had a planet A being orbited by moon B, would not a further moonlet orbiting C have the possibility of orbiting planet A as well in a figure of 8 pattern?Not without frequent course corrections: that sort of "cycler" orbit can't persist, because of the relative movement of the two main bodies.
However, figure-of-eight orbits involving three (equal-mass) bodies are possible, if they chase each other around the figure-of-eight. Here (http://www.bdl.fr/Equipes/ASD/preprints/prep.2000/huit.pdf) is the "discovery paper".

Grant Hutchison

tony873004
2007-Nov-12, 11:23 PM
There's other strange but stable configurations as well. Descriptions, animations and links to papers are available in this thread on my forum:

http://www.orbitsimulator.com/cgi-bin/yabb/YaBB.pl?num=1181200864

Kaptain K
2007-Nov-15, 03:58 AM
A "two body" capture won't work, but as tony873004 said earlier, a "three body" capture could happen.