Re: [Phys-l] Binary star question

[Jack Uretsky <jlu@hep.anl.gov>]

	The most elegant, and clear, discussion of the Kepler problem that 
I know, due, I believe to Cal Tech's mathematician Tom Apostoli, is in the 
textbook <The Mechanical Universe>, the edition by Olenick, et al., 
Chapteers 26-29 (Chapter 27 discusses eccentricity).
	One way to loook at it is that for fixed angular momentum, the 
circular orbit is the orbit with minimum energy (assuming a 1/r 
potential).
					Regards,
						Jack




On Sat, 29 Dec 2007, Savinainen Antti wrote:

> Hi,
>
> I have a problem with one detail in quite a simple exercise.
> It goes like this. Two stars are revolving in circular orbits
> around their common center of mass. The masses are given and it
> is told that their mutual distance remains constant (this distance also given). The period is asked; with the above mentioned
> assumption they have the same periods.
>
> Now this is not hard to do and I have no problems with solving
> the exercise. I just can't see why their mutual distance remains
> constant. I suspect it follows from a conservation law (angular momentum?). Help would be appreciated as always :-).
>
> Best wishes,
>
> Antti

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