Infrared Knots Around SS433 -- Results of Jets

SS433 is a famous exotic object in the center of radio source W50. It has been widely observed at various wavelengths and has attracted more and more attention since 1978. The most unusual feature of SS433 is two relativistic jets ejected at a velocity of 0.26c in opposite directions (MARGON [1]). This feature can explain the simultaneous presence of red and blue shifts of strong optical emission lines varying periodically as well as the two bright X-ray lobes stretched in the direction of the jets (SEWARD et al. [2]). In 1987, six infrared knots around SS433 were discovered from IRAS data by BAND [3]. They have similar infrared spectra except for the fifth one. Band suggested that the fifth one is a different kind of object [3], and we agree. But for the other five knots, we suggest a different model. We don t think it is accidental that five knots are all located in the direction of the jets and are within, or adhere to, the radio shell of W50. It is very probable that they result from the interaction between the jets and the interstellar medium. We assume that the knots consist mainly of dust grains and gas. Both are continuously heated by collisions of particles in the jets. Their spectra are explained by the thermal radiation of dust grains and the free-free emission of partly ionized hydrogen gases.