[math-fun] Is this the Guinness record refraction index?

WDS> It is estimated that heat produced in sun core takes 200K years to escape, http://articles.adsabs.harvard.edu/full/1992ApJ...401..759M/0000760.000.html since the sun's gas is a thick layer of insulation that slows down radiative transfer.<WDS "The average velocity of the photon between the center and the inner edge of the convective zone is v = ... = .97 cm/s". ! Can someone save me researching what inhibits convection inside this zone? --rwg