Imaging of radio supernovae

As the shock and expanding shell of a supernova plow out through the circumstellar material at thousands of km s(-1), radio emission is generated. VLBI observations of this radio emission are presently the only means to directly image the expanding shell of any supernova much farther away than SN 1987A. The last decade has seen great progress in VLBI imaging of radio supernovae. In particular, SN 1993J in the galaxy M81 provided a rare opportunity to closely study an expanding supernova, and has been intensively observed. I summarize some of the results on SN 1993J and other radio supernovae, and compare the different observed radio supernovae. I briefly discuss the future prospects of radio supernovae imaging.