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Why are planetary nebulae linked to white dwarf stars rather than supernova explosions?

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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.

Planetary nebulae are linked to white dwarf stars because they represent the final evolutionary stages of intermediate- and low-mass stars, rather than the catastrophic, explosive deaths associated with supernovae.1

The formation of a planetary nebula is a gradual process occurring near the end of a star's second red giant phase. During this time, the star becomes unstable and sheds its outer, hydrogen-rich atmosphere through stellar winds and the ejection of an envelope. This process leaves behind a dense, hot, and luminous core—the progenitor of a white dwarf. As this core contracts and heats up, it emits ultraviolet radiation that ionizes the previously ejected gas, creating the glowing shell we observe as a planetary nebula.2134

In contrast, supernovae are explosive events that typically involve more massive stars or specific binary systems. While white dwarfs can play a role in certain types of supernovae (such as Type Ia), the planetary nebula phase itself is a non-explosive transition that allows a star to gently transition into a stable, cooling white dwarf remnant.13