A planetary nebula is not formed like other types of nebula such as the Pleiades, Bubble, etc:
“A planetary nebula is created when a star blows off its outer layers after it has run out of fuel to burn. These outer layers of gas expand into space, forming a nebula which is often the shape of a ring or bubble.”
What is a planetary nebula?
coolcosmos.ipac.caltech.edu
A star could produce a planetary nebula as part of its death throes before collapsing to form a BH or WD. Or it could continue to burn as a conventional star, but slimmed down a bit. Wish I could do the same to get rid of this Covid waistline!
I got my first Elite badge, Exploration, in a 26ly Cobra. But I now prefer my 60ly armed Phantom for everyday use.