Asymmetries in core-collapse supernovae from maps of radioactive ⁴⁴Ti in Cassiopeia A

http://www.nature.com/nature/journal/v506/n7488/full/nature12997.html

(1st sentence) 

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. 

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(Last sentence)

As neither the spherically symmetric nor the strongly asymmetric explosion reproduces all of the observed properties of the ⁴⁴Ti spatial distribution, the progenitor of the Cas A remnant was most probably between these two extremes: a mildly asymmetric explosion developing low-mode convection.