Here's why:

* Brightness is relative: Brightness can be measured in terms of absolute magnitude (intrinsic brightness) or apparent magnitude (how bright something appears from Earth).

* Absolute Magnitude: Vega is actually more intrinsically luminous than the Sun. It's a hotter and larger star.

* Apparent Magnitude: The Sun appears much brighter from Earth because it's much closer to us than Vega. Vega is about 25 light-years away, while the Sun is only 8 light-minutes away.

So, while Vega is a more powerful star in terms of its own light output, the Sun appears much brighter to us due to its proximity.