Fast Low-Ionization Emission Region

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Fast Low-Ionization Emission Regions (FLIERs) are volumes of gas with low ionization near the symmetry axis of many planetary nebulae. Their outflow speeds are significantly higher than the nebulae in which they are embedded, and their ionizations are much lower.

FLIERs' high speeds suggest ages much younger than their parent nebulae, and their low ionizations indicate that the ultraviolet radiation that ionizes the gas around them does not penetrate into the FLIERs.

No current model of stellar or nebular evolution explains FLIERs.