This is though only a guess.

I believe the green “streaks” are stars that are moving and leaving behind a trail of hot gas. Don’t quote me on that, though.

Curse these pathetic human eyes.

Someone at NASA made a photshop of how big the Moon is relative to M31, assuming M31 was bright enough for us to see like this. Hopefully this gives those asking a visual reference.

Intensely cool image! Go & Digg it!

Baka & Dan: You’re right, this thing is large. However, you can just see a dim smudge with the naked eye, which is the core of the galaxy. No details, unfortunately, as the spiral arms are just too dim for our eyes to make an image. You can take a nice picture of this galaxy with a little practice, some modest equipment & some dark skies. A zoom lens of 200 – 300 mm is sufficient, no telescope needed. A tracking mount, is required, though. A large telescope with a low power eyepiece will show some detail, but this is expensive.
Here’s my latest feeble try with a 135mm telephoto:

I’ll stick with Cat’s Eye Nebula (NGC 6543) for my wallpaper. It’s an image that just keeps on giving.

“…the full Moon would just fit over the apparent size of the central bulge of the galaxy.” Does that mean that if we could see this image in the sky with the naked eye, and the full moon happened to eclipse the center bulge, we’d still see these huge spiraling arms dominating much of the sky!? Freaking wow!

Phil this blog is great!