“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.)

I don’t know if we’d say the same if this happened to US.

Or, if the HTML doesn’t work:

That first picture looks awfully familiar:

http://antwrp.gsfc.nasa.gov/apod/ap070819.html

Here’s a link to ARP 148 (topmost picture in Phil’s post) from that Atlas:
http://nedwww.ipac.caltech.edu/level5/Arp/Figures/big_arp148.jpeg

This link is on the Hubble Web site’s page along with a link to the Arp Atlas on a Cal Tech Web site.

Wow! and Wow!

How can one reject study of the natural universe, when it presents us with wonders such as these?

So the milky way is going to collide with Andromeda some time from now. What kind of collision will that be? Is that known? I mean, what is the angle of impact and so on?