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What causes faint rings around some planetary nebulae?

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Planetary nebula Southern Ring Nebula as captured by the James Webb Space Telescope in the near-infrared (left) and the mid-infrared (right). The dimmer star at the center of this scene has been sending out rings of gas and dust for thousands of years in all directions. The Southern Ring Nebula is approximately 2,500 light-years away.

Faint rings observed around some planetary nebulae are the remnants of a previous shell of material that was ejected by the star at an earlier stage in its evolution.1

Before a star forms a planetary nebula, it passes through a red giant phase, during which it experiences significant mass loss through a relatively slow-moving stellar wind. These faint, surrounding rings represent this earlier expelled material, which remains visible even as the star continues its transition toward becoming a white dwarf star.12