Here's why:

* Main-sequence stars are stars that are fusing hydrogen into helium in their core. This is the longest and most stable phase of a star's life.

* Black dwarfs are the theoretical end state of a white dwarf that has cooled down completely and no longer emits any light. Our Sun is not even close to this stage.

The Sun is about halfway through its main-sequence lifetime, which is estimated to be around 10 billion years. After this phase, it will become a red giant, then a white dwarf. It will take many billions of years for it to cool down enough to become a black dwarf, a process that hasn't even begun yet.