Everyone has heard of the Andromeda Galaxy, Messier 31 but many don’t realize just how big the galaxy is in our sky. It’s so large that it doesn’t fit in the field of view of many telescopes, including this one which can’t quite manage 50% of it. At more than three degrees across on the long side, it’s apparent size in our sky is larger than six full moons across!

At that size you might wonder why you can’t see it with your unaided eyes. And, the answer is you can if the sky is dark enough. It’s a fairly easy target to find with binoculars. With visual telescopes, unlesss you are in a dark sky, it can be a bit disappointing to look at. But, put a camera on even the smallest of telescopes and you a see amazing detail. What’s more is that detail is more than two and a half million light years away but it’s getting closer by 110 kilometers per second. In four billion years, our Milky Way and Andromeda are set for an amazing merger!

This image looks at the southern half of the galaxy (southern from the perspective of our sky). The dust lanes and nebulae in the galaxy are clear to see along with one of Andromeda’s small satellite galaxies, Messier 32.

What amazes me is just how bug and how much we can see into M31. Large enough telescopes can even resolve individual stars in it! Our galaxy and M31 are of a similar size, M31 might be a bit bigger but it is now thought that M31 is a bit less massive and the Milky Way a bit more massive than estimates from the late 20th century so in once sense this is like looking in a mirror. Our galaxy won’t look exactly like this but should be somewhat similar.

This is 33h 20m of HaLRGB data. For all the technical details see astrobin.