> I can imagine that scientists have figured out accurate ways to measure the "actual" brightness of stars Sure. This is actually pretty simple. Stars visible

> I can imagine that scientists have figured out accurate ways to measure the "actual" brightness of stars Sure. This is actually pretty simple. Stars visible with naked eye are relatively close to us. We can measure parallax (https://en.wikipedia.org/wiki/Stellar_parallax https://en.wikipedia.org/wiki/Stellar_parallax) and this gives you the distance to the star directly. Once you know the apparent brightness and the distance you can calculate the actual brightness. "The Hubble telescope WFC3 now has a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to 3,066 parsecs (10,000 ly) for a small number of stars." Vast majority of visible stars fall within couple thousand light years, the only ones that are further are extremely bright, extremely rare and extremely short lived.