De58te wrote:In the expanded view next to the galaxy pointed out by Coil Smoke, there are two neat blue galaxies really close to each other. I wonder if they are colliding?
Also look at the neat all red galaxy just above the ESA letters. I wonder why the galaxy is all red. Could it be due to the expansion of the universe and all the distant galaxies are red shifted because they are moving away from us? There are about 2 or 3 other red galaxies along the bottom, but through the rest of the photograph the galaxies are either white or blue. There are a lot of blue distant galaxies visible. Would those galaxies be blue shifted because they are all moving towards us? That would be at odds with the distant galaxies being red shifted.
Well, the two most obvious galaxies that I can see, that are definitely interacting and close to the "pale bright ghost galaxy" at upper right - I like that desciption
- aren't blue, but yes, they really seem to be interacting. So yes, they should collide in a few (hundred) million years from now. (And of course, if we could see what these galaxies have evolved into hundreds of millions of years after the light that we can see actually left them - which we can't - we would probably see that they have already collided.)
The very red background galaxies do indeed owe their color to redshift reddening, although it is quite possible that dust reddening also contributes to their color.
The very blue galaxies, by the way, were forming hot bright stars at a furious rate at the time when the light that has reached us left them. At that time they emitted copious amounts of ultraviolet light, which has since been redshiftet into the blue light that we now can see.