The origin of the strings in the outer regions of η Carinae

The narrow optical filaments (‘strings’ or ‘spikes’) emerging from the Homunculus of η Carinae are modelled as resulting from the passage of ballistic ‘bullets’ of material through the dense circumstellar environment. In this explanation, the string is the decelerating flow of ablated gas from the bullet. An archive Hubble Space Telescope image and new forbidden-line profiles of the most distinct of the strings are presented and discussed in terms of this simple model.