Does the blue shift of the Andromeda Galaxy contradict Big Bang cosmology?

Answer 1

No, it doesn't. The Big Bang is about the LARGE scale structure of the universe and its expansion. On these scales, the Andromeda galaxy is *very* close to us! The 100 Km/sec that the Andromeda galaxy is approaching us is called 'peculiar motion' and a similar motion also happens with a couple of the galaxies in the Virgo cluster (which is also close to us on the scale of Big Bang physics).

On way to think of this is that the Milky Way and the Andromeda spiral are gravitationally bound along with a few other galaxies to form the Local Cluster. For the Big Bang, it is how the different *clusters* are moving away from each other. Inside of the different clusters, the individual galaxies are orbiting. So other galaxies in our cluster can be moving toward us and some galaxies in other clusters can be also *if* they are orbiting in the right way in their cluster. For clusters more distant than the Virgo cluster, the overall expansion outweighs the peculiar motions of the orbits and everything has a net movement away from us. We still see a spread of velocities within each cluster due to the orbits.

Answer 2

I've never heard that Andromeda is blue-shifted, but it could have something to do with the fact that it's racing towards our galaxy. However, the velocity may not be great enough for that to be the cause of a detectible blue-shift.

Answer 3

Mathematician has hit it on the head. Incidentally, the Milky Way and Andromeda are heading for a merger in the next Gyr or so.

The site below has some discussion and best of all some animations of multiparticle simulations (computer models) of the event.

Answer 4

If the galaxy is blue-shifting, that means its coming closer, while the big bang states everything is moving away.

Answer 5

Andromeda has a blueshift? I never knew that... But no, I don't think so. I think our galaxy is farther from the center of the universe than andromeda is...