Here's why:

* Supergiants are incredibly massive stars, often hundreds or even thousands of times more massive than our Sun. They are extremely luminous, radiating vast amounts of energy.

* White dwarfs, on the other hand, are the remnants of stars like our Sun after they have exhausted their nuclear fuel. They are much smaller and cooler than their progenitor stars. While they are incredibly dense, their surface area is small, meaning they emit far less light.

In general, supergiants are far, far brighter than white dwarfs.

However, it's worth noting:

* Distance matters: A very close white dwarf could appear brighter than a distant supergiant.

* Luminosity is not the same as apparent brightness: A white dwarf might be intrinsically less luminous than a supergiant, but it could appear brighter to us if it's closer.

Let me know if you have any other questions about stars!