Editing SSC/FreeEnergy/EquilibriumSequenceInstabilities (section)

====Tassoul (1978)====
From p. 449 of [<b>[[User:Tohline/Appendix/References#T78|<font color="red">T78</font>]]</b>] &#8212; ''verbatum'' text in green:  <font color="green">
Let the masses of the primary and the secondary be <math>~M</math> and <math>~M^'</math>, respectively; let the distance between their centers of mass be <math>~d</math>; and let the angular velocity of rotation about their common center of mass be <math>~\Omega</math>.  Next choose a system of reference in which the origin is at the center of mass of the primary; for convenience, the <math>~x_1-</math>axis points toward the center of mass of the secondary, and the <math>~x_3-</math>axis is parallel to the direction of <math>~\vec\Omega</math>.  Then, the equation of the rotation axis, which of course passes through the center of mass of the two bodies, is
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<math>~x_1 = \frac{M^' }{M + M^'} ~d</math>
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&nbsp; &nbsp; &nbsp; and &nbsp; &nbsp; &nbsp; 
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<math>~x_2 = 0 \, .</math>
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Accordingly, the centrifugal force acting on the mass <math>~M</math> may be derived from the potential
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<math>~-\frac{1}{2}\Omega^2\biggl[ \biggl( x_1 - \frac{M^'}{M + M^'} ~ d\biggr)^2 + x_2^2\biggr] \, .</math>
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