Stellar formation: Shaping by dynamo

Attempts to account for the formation of asymmetric planetary nebulae have suffered from a persistent problem: a magnetic field could generate the observed shapes, but how to generate such a field? Blackman et al. propose that the answer lies in dynamo action between the core of the associated AGB (asymptotic giant branch) star and its more slowly rotating outer layers. This new dynamo-based model can also explain the puzzlingly slow rotation of most white dwarf stars (products of the AGB phase), by invoking magnetic braking of the stellar core.

Dynamos in asymptotic-giant-branch stars as the origin of magnetic fields shaping planetary nebulae
ERIC G. BLACKMAN, ADAM FRANK, J. ANDREW MARKIEL, JOHN H. THOMAS, HUGH M. VAN HORN
Nature 409, 485-487 (25 January 2001)
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25 January 2001 table of contents