Space images and light-year per pixel.?

Question

When we look at a picture of a galaxy, how is it possible that we see dish, like galaxies in a near perfect circle (ok, with an angle due to the point of view). There is a huge disparity of distances of light sources from the closes point to us and the farthest point from us. We look at a picture on a computer, and the pixel to the side corresponds already to quite a few thousands of light-years away (specially on galaxies photos).
I think that light from the farthest point of the galaxy would be messed up due to the time span, and other light sources. There should be a sort of a time-caused lag on the image related to light travel, and we don't see that lag.

Answer 1

You are confusing a few things.

Galaxies are very slowly evolving objects. For instance, at the distance the sun orbit our galactic core, it goes around in about a quarter billion years. Yet the galactic diameter is "only" 100000 light years, so for all intents, one may consider that stars would essentially not have moved -- only 1/2500 of their orbit -- when the light from the furthest one gets to the location of the closest ones.

Answer 2

Keep in mind the scale of the distances and the inverse square law. Light intensity we perceive is a function of 1 divided by distance squared.

Now lets put a galaxy's near side 1000 light years away and we notice its brightness. Then we look to the far side 2000 light years away and we'll see that end of the galaxy 1/4 as bright as the closer edge.

Now, lets put the galaxy's near edge to 10,000,000 light years away. Now the far edge is 10,001,000 light years away. The far edge is now (10,000,000 / 10,001,000) squared as bright which is .9998 dimmer. It's a scale of distance. When you get to something a long distance away, it's dimension is so small a part of the distance that it's in the noise.