The bubble-like interior of the core-collapse supernova remnant Cassiopeia A

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Science  30 Jan 2015:
Vol. 347, Issue 6221, pp. 526-530
DOI: 10.1126/science.1261949

Burbling explosions blow metallic bubbles

Stars more than about eight times the mass of the Sun don't go out quietly. Asymmetric explosions are kicked off by the collapse of their iron cores when no more fusion energy can sustain them. Exactly how this stellar catastrophe proceeds is difficult to probe. Milisavljevic et al. have now peered into the supernova remnant Cas A in the near-infrared and present a three-dimensional map of its interior unshocked ejecta. The bubble-like structure points to turbulent mixing, which may help us understand other supernova remnants whose structure cannot be seen in such detail.

Science, this issue p. 526


The death of massive stars is believed to involve aspheric explosions initiated by the collapse of an iron core. The specifics of these catastrophic explosions remain uncertain, due partly to limited observational constraints on asymmetries deep inside the star. Here we present near-infrared observations of the young supernova remnant Cassiopeia A, descendant of a type IIb core-collapse explosion, and a three-dimensional map of its interior unshocked ejecta. The remnant’s interior has a bubble-like morphology that smoothly connects to and helps explain the multiringed structures seen in the remnant's bright reverse-shocked main shell of expanding debris. This internal structure may originate from turbulent mixing processes that encouraged outwardly expanding plumes of radioactive 56Ni-rich ejecta. If this is true, substantial amounts of its decay product, 56Fe, may still reside in these interior cavities.

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