From: areynold@estsa2.estec.esa.nl (Alastair Reynolds)
Subject: Re: (whorl) Double planets
Date: Mon, 13 Jul 1998 15:00:38 +0200 (MET DST)

Peter:

> 
> Unfortunately, I don't think Blue and Green *have* a Lagrange point.
> Hal Clement has a short story called "A Little Knowledge", in which
> a fleeing criminal parks his spaceship what he fondly imagines is
> a Lagrangian point of a double star. But the two stars are too closely
> matched in mass for it to work: one mass has to be considerably bigger
> than the other. (If anyone has the story, and the ratio is 25.8 : 1,
> then I shall appear very clever; if it isn't, well, how can I be expected
> to remember a detail like that?) The story ends with the fugitive
> finally getting round to looking out of the window, to find himself
> plunging into one of the stars as it orbits towards him.
> 

actually, any two orbiting point masses will always have five lagrangian 
points around them; the one between them (exactly in the middle for equal 
masses) is L1. L1 isn't stable - something placed at L1 only needs a 
tiny nudge in either direction and off it goes. 

The point HC might have been making is that L4 or L5 (the "usual" Lagrange 
points, off to either side) might only be stable if the ratio is as above?

blimey - the first thing on the list I've responded to in ages!

al

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