Instabilities and nonradial motion in SN 1987A

Detailed numerical calculations of relatively high resolution show that shock propagation through realistic presupernova structure results in a pronounced Rayleigh-Taylor instability. We find processed matter penetrating near to the H-He interface after only 10^4^ s, well before significant decay of ^56^Ni, and pronounced fingers forming in density (though not in temperature). Such behavior has profound implications for line formation, polarimetry, and X-ray and γ-ray emission from supernova 1987A, and for the subsequent development of the Ni-Co "bubble." These results are consistent with previous work on less realistic structures published by Muller et al. in 1989 and Chevalier in 1976, and inconsistent with work published by Nagasawa et al. in 1988.