Giant stars such as Betelgeuse may appear to dwarf our Sun, but their densities are so low that they are basically red hot vacuums.
A Darker Edge
When you look at an image of the Sun, you might notice that it’s edge appears slightly dimmer than its center. This is an effect known as limb darkening, and its actually quite useful to astronomers.
Star Light, Star Bright
The brightness of a star depends not only on how bright it actually is, but also on how far away it is. This is why we use quantities such as apparent magnitude and absolute magnitude.