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Planetary Nebulae have NOTHING to do with Planets. A Planetary Nebula is a shell of hot ionized ga
s (seen in atomic emission lines) expanding away from the very small,
very hot, central star.
This central hot star is the former red giant core. It is called a
WHITE DWARF.
The timescale for the Planetary Nebula stage is ~20,000 years (very short). However, there are so many stars in our Galaxy, we can find many stars currently passing through this very interesting stage of evolution. By studying OTHER solar-mass stars, we have learned how our own sun will evolve.
