Acceleration and thermal instabilities in the jets of SS 433

A discussion is presented for the way in which unique characteristics of the peculiar object SS 433 can be interpreted by a beam model in which light jets are accelerated by radiation pressure and collimated within the funnels of an accretion disk, formed around the compact component of a binary system, and, during their propagation outside the funnels, are fragmented into denser clouds via thermal instabilities. It is shown that it is possible to explain the observed blue and red-shifted H-alpha line emission in terms of thermal emission from the clouds embedded in the jets and moving at the typical speed of 0.26 c that is determined by the physical characteristics of the accretion funnels (as temperature, central mass, opening angle, etc.). The conditions for instability and cloud evaporation set a limit on the region along the jet where optical line emission can occur, and this result agrees remarkably with observations.