  We revise a problem of the birefringence of electromagnetic waves in a chiral
medium in the Standard Model (SM) of particle physics arising in an isotropic
plasma due to parity violation. The recent calculations of the weak correction
to the photon polarization operator in electroweak plasma allow significantly
to improve some previous estimates of such effect in astrophysics.
Nevertheless, it has remained beyond the abilities of the present technics yet.
