When does bipolar flow occur?

Question

When does bipolar flow occur?

Answer 1

You have two answers that seem to conflict - so let me bring it together.

Young stellar objects - i.e. stars in the process of forming have bipolar flows that are a result of accretion.

The visible manifestation of these things are sometimes called Herbig-Haro objects.

Dying stars also have bipolar structures - although it is not clear whether they all do this, or even whether its a flow.

Certainly they seem to develop toroidal (donut-shaped) dust rings that may collimate a flow - or may just make them look bipolar because light can escape more easily along the axis of the donut.

Other astrophysical environments have bipolar structures too.

Answer 2

before the star actually gets hot enough to ignite nuclear fusion, an intense stellar wind is generated. because the cloud was slowly rotating, a disk of material forms around the star. the disk collimates the intense stellar wind into 2 oppositely directed beams producing what is referred to as a bipolar flow.

Answer 3

A stream of matter in two opposing directions from a central object, usually a star. Bipolar flows represent significant periods of mass loss in a star’s life. They tend to occur during the protostar and pre-main-sequence phase and, again, during the red giant phase just before the production of a planetary nebula.