Here's why:

* Planetary nebulae are formed when a star like our sun runs out of fuel. The star sheds its outer layers, creating a beautiful cloud of gas and dust.

* The core of the star remains, incredibly dense and hot, and is called a white dwarf.

* The white dwarf slowly cools down over billions of years, eventually becoming a black dwarf.

So, while the beautiful planetary nebula is gone, the leftover white dwarf is a fascinating object in its own right, marking the end of a star's life.