Continuum observations of IC 443 were made at 21 cm with a resolution of 23″×59″. The appearance in the radio continuum is very similar to the optical appearance. Since the radio emission is nonthermal, this requires a mechanism that can enhance the synchrotron volume emissivity within thermal filaments, which emit strong optical radiation. We suggest compression of gas and magnetic fields in a shock.
Tycho's remnant has been observed both at 21 cm (resolution 24″ × 27″) and at 6 cm (resolution 7″ × 8″). Most of the fine scale structure is resolved. The similarity at the two wavelengths indicates a remarkable constancy in the spectral index of features down to a scale of 20″.