I am confused as to what the Chandrasekhar-Friedman-Schutz (CFS) instability is, exactly. It seems to refer to this paper by Chandrasekhar, but I do not think this paper covers the full instability. In the first part of the paper, Chandrasekhar shows that a Jacobi ellipsoid radiates off angular momentum in gravitational waves to become a Maclauren ellipsoid. I do not yet understand the second part of the paper.
This webpage says that in a rotating star, a non-axially symmetric perturbation rotating slower than the star will radiate off angular momentum, thus increasing the size of the perturbation. Apparently, any rotating star is unstable in general relativity because of this mechanism.
Questions: I am very confused as to what the exact nature of the instability is. Do quickly rotating stars collapse into black holes, or do they just radiate off angular momentum and settle down into slowly rotating stars? Have we detected this instability experimentally in the real world? Moreover: damping effects (like friction) in a real star work against the instability in slowly rotating stars. Can they fight the instability also for fast rotating stars?
Also, is there a good source that gives an introduction to the instability? Papers by Friedman and Shutz (for example, this one) seem to focus heavily on obtuse mathematics (i.e. "trivial" Lagrangian perturbations) and don't present a clear physical picture of what the instability actually is.
