For
a (very luminous) hot star, this can compete with gravity…but note the 1/R2 dependence, if arad > agrav, a star would blow itself completely apart.
But
note, free electron opacity, and the associated
Thompson scattering, can be significantly
augmented by absorption of photons in
spectral lines
- atoms act like a resonance chamber
for electrons: a bound electron can be ‘driven’
much more efficiently by light than a free one (i.e. it has a much larger cross section), but
it can only be driven by light with a very
specific frequency.