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Posted by rob on November 30, 2006, 3:49 am
Please log in for more thread options Say, I saw a summary of that paper in the magazine "The New Scientist" a
couple of months ago :)
>>>-> It's your turn.
>>> -> Regards
>>> -> Ken
>>>
>>> Well, remember that the systems we are talking about are strictly
>>> reversible. If you run a sim and a star gets ejected from orbit, then
>>> you can run it the opposite way and the star gets captured.
>>> Generalizations about the ways in which the systems evolve are highly
>>> suspect - at least when the stars are of equal mass.
>>>
>>> If the masses are unequal, then equipartition of energy becomes an
>>> important concept. Statistically, over a long time, the bodies' average
>>> energies tend to be equal. This means that the lighter bodies move
>>> faster, on average, than the more massive ones, so the lighter ones are
>>> most likely to move at more than escape velocity, and are therefore
>>> lost from the system. The energy they take with them is removed from
>>> the remaining bodies, which therefore tend to crowd closer together.
>>>
>>One thing that writing this sim has shown me is that capturing an object
>>seems to be very hard. I sometimes wonder how it is that we could
>>speculate
>>that a moon could be captured and yet end up in an almost circular orbit
>>(such as Triton). I assume that something must influence the moon after
>>its
>>capture that then forces it into a more circular orbit?
>>
> That's the easy bit - tidal forces will do it.
> But the initial capture is indeed very difficult. There was a recent paper
> on Triton's capture
> <http://www.nature.com/nature/journal/v441/n7090/abs/nature04792.html>
> I'll expect correction but I'm not convinced that these systems are always
> strictly reversible". Doesn't capture usually require some deceleration of
> the captured body, as when a probe enters orbit around another planet?
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