Here's why:
* Stars evolve: Stars go through different stages in their life, and planetary nebulae form during the final stages of a star's life.
* Red giants and white dwarfs: When a star like our Sun runs out of hydrogen fuel in its core, it expands into a red giant. Eventually, the outer layers of the star are ejected, creating the beautiful, expanding shell of gas and dust we call a planetary nebula. The remaining core of the star becomes a white dwarf.
* Not a single object: A planetary nebula is not a single, cohesive object like a star. It's a cloud of material expanding outwards, eventually dispersing into space.
So, while the planetary nebula was once part of a star, it's not the star itself anymore.
