Clearly the fields produced by the vortex are creating the compressed appearance. A galaxy serves as a good example for this same basic energy flow. Each vortical field has unique properties and can form the familiar spherical field or it can form a flatter disc-like field or the conical hourglasses seen which are assumed to be the death of stars, but which are more accurately described as really a polar vortex of energy changing its relationship with space.

So in a nutshell, vortical motion of the star's core vortex and it's emitted field is the cause of the 'flat' appearance.

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