“After classifying thousands of galaxies on the Galaxy Zoo website, I have to admit that the last one looks to be 3 galaxies instead of two. The third, in the top middle can be a star forming region I suppose, but there looks to be a clear bar like structure that may represent a galactic core. Does anyone know more about this particular interaction? How are we certain there are only two galaxies instead of three?”

My guess – maybe those extra ones could possibly be background ‘line-of-sight / chance’ galaxies – not one’s directly involved in the collision?

We’re looking at galaxy clusters and superclusters here so many galaxies at slightly differing distances in a relatively small area of sky .. Hmm .. I’m not really sure though ..

“I wonder how that story will end; lover’s embrace or ships passing (literally) in the night?”

Literally?? Oh dear, sorry to be a grammar / lexicon nazi (& yeah, I’m ofetn lousy whenitcome stogrammar & don’t even start on typos) but .. Argh! NO! No & again no!

‘Night’ (and ‘day’) are in this context totally inapplicable words.

Ships = galaxies???

NO! Not literally! ;-(

Metaphorically sure but not literally.

So they’re colliding and maybe pasing each other like galaxies in the cosmos not ships in the night.. Literally speaking.

*Metaphorically*, like ’ships in the night’ .. okay. Bit of a cliche but okay.

Still thanks Bad Astronomer for those awe-inspiring, breath-taking, thought-sparking images.

I’m thinking they’ll have to be in 2008’s top 10 astro-images .. !

On average, the galaxies are moving apart. But since they’re not actually embedded in a cake, they’re free to have their own individual motions, superimposed on the general expansion.

Most galaxies are in gravitationally bound clusters. I *think* that galaxies within a cluster don’t tend to move apart; rather, the clusters are moving away from each other. Thus the number of collisions is probably about the same as it would be in a hypothetical non-expanding universe. (This is about 80% speculation on my part.)