The Dynamical Development of the SN 1987A Ring Nebula

Abstract

Continuing observations show the structure of the 3 arcsec environment of SN 1987A to be surprisingly regular. There is now little doubt that the brightest part of the nebula is highly axially symmetric, possibly a pure ring. The understanding of this structure is a challenge to current nebular formation theories, and may perhaps lead to a better understanding of similar structures such as planetary nebulae (PNe) and the ring nebulae around Wolf-Rayet stars. This study thus intends to investigate from a theoretical point of view how a ring-like nebula can form.

The physical scenario adopted for this study is the interaction between the slow wind ejected by the SN 1987 A progenitor while it was a red supergiant (RSG) and the fast wind emitted later as the star evolved to a blue supergiant (BSG). In our model, an initially very small seed asymmetry in the RSG wind is magnified, and observable axially symmetric nebular structures, or even rings, are produced, We argue that the SN 1987A ring nebula is not unique, and the formation f highly axially symmetric nebulae (and of rings) should be quite a common phenomenon in nature, as confirmed by the fact that only a very small fraction of the observed circumstellar nebular appears to be a spherically symmetric.