Why do massive stars form bow shocks? Bulk ISM motion as the main driver of bow shock formation and geometry

Bow shocks are one the most commonly observed impact sites of massive star feedback.

Bow shocks are one the most commonly observed impact sites of massive star feedback. Their existence is often taken as evidence of the supersonic motion or even runaway nature of the massive star. Bow shock geometry is also used to infer the properties of the stellar wind.…