A couple things to keep in mind: Andromeda is so big that to see it, you're looking through a large portion of the Milky Way. Some of the really bright looking

A couple things to keep in mind: Andromeda is so big that to see it, you're looking through a large portion of the Milky Way. Some of the really bright looking stars in this picture are actually in the Milky Way. There is a ton of space between stars, but they're also not completely flat. It's less like a sheet of paper and more like a thick pancake. So-called "empty" space isn't empty. Some of it is mostly just a vacuum, but lots of empty space is filled with gas which is glowing due to latent light/heat/radiation. In that regard, parts of this picture are glowing similarly to shining a flashlight in fog. Even if you managed to zoom in close enough to an empty spot between stars in our galaxy, which also was an empty spot between the stars and gas in Andromeda, you would still start seeing the distant galaxies far beyond Andromeda. The Hubble Deep Field [1] is a good demonstration of this effect. They pointed the Hubble at a previously thought "empty" region of space and held it there for about 10 days. After gathering all the received photons collected over that time into a single image they realized that even "empty" space is full of a lot of stuff if you look far enough out. [1] https://en.wikipedia.org/wiki/Hubble_Deep_Field https://en.wikipedia.org/wiki/Hubble_Deep_Field