What atomic process generates the observable light emitted by the energized gas cloud?
Answer
Electrons recombining with atomic nuclei, releasing photons at specific wavelengths
When ionized electrons recombine with atomic nuclei in the expelled shell, they cascade down energy levels, releasing photons, which is the light observed as the nebula's glow.

Related Questions
What mass range defines the stars that evolve into planetary nebulae?What object remains at the center of a planetary nebula providing the energy for its glow?What primary physical process is responsible for making the ejected shell visible as a nebula?How long does the visible phase of a planetary nebula typically last on astronomical timescales?What atomic process generates the observable light emitted by the energized gas cloud?What factor in the progenitor star's environment often leads to complex, non-spherical planetary nebula shapes?Why were these objects historically given the misleading name 'planetary nebula'?How does the illumination mechanism of a planetary nebula differ fundamentally from a reflection nebula?What specific chemical element's strong emission is often responsible for younger, highly ionized nebulae appearing blue-green?If a bipolar planetary nebula is viewed exactly pole-on, what shape might its visibility suggest?