Understand
Overwhelming evidence has accumulated in recent years that supernova explosions are intrinsically 3-dimensional phenomena with significant departures from spherical symmetry.
- We review the evidence derived from spectropolarimetry that has established several key results: virtually all supernovae are significantly aspherical near maximum light; core-collapse supernovae behave differently than thermonuclear (Type Ia) supernovae; the asphericity of core-collapse supernovae is stronger in the inner layers showing that the explosion process itself is strongly aspherical; core-collapse supernovae tend to establish a preferred direction of asymmetry; the asphericity is stronger in the outer layers of thermonuclear supernovae providing constraints on the burning process.
- We emphasize the utility of the Q/U plane as a diagnostic tool and revisit SN 1987A and SN 1993J in a contemporary context.
- An axially-symmetric geometry can explain many basic features of core-collapse supernovae, but significant departures from axial symmetry are needed to explain most events.