The Hubble picture of ARP 194 made me wonder about what actually happens when galaxies collide, merge or what would the best word be? We've seen them seemingly pass through each other, being left with much distortion. And I've read that collisions of stars would be rare, because there are still light years of empty space between them. But statistically, billions of stars within dozens of light years ought to yield quite a few collisions. Do we have any idea how many, or what actually happens when stars collide?

(Let's assume for now that the black holes go their own ways.)

This might help.

http://en.wikipedia.org/wiki/Blue_straggler

http://www.solstation.com/x-objects/bluestrag.htm

I dont believe there is any direct observational evidence of what happens when stars collide, but the blue straggler theory seems to be gaining support as a possible result of stars getting together.

Statistically the chances of two stars hittng each other during a galactic encounter are exceptionally low, but as the old saying goes. Never say never. Our chances of obseving such an encounter with any detail would be infantesimal

Wait a minute!
See, Andromeda is coming soon, at a co-ordinate near you!
http://en.wikipedia.org/wiki/Androme..._Way_collision

No seriously though, MAPNUT, there are a few threads here, which have delved into this area.
In fact I filed (so safely, i don't know where) a link, from one of the posts on a particular thread, recently, which has a computer generated sequence of such phenomenal cosmic events. I can't for the life of me, remember who provided that link.

You could do BAUT search to take you there. I'll try locate it for you, unless some one kinder and faster, here, beats me to it. I wouldn't be surprised.

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clear skies

If you want to make an apple pie from scratch, you must first create the universe. CARL SAGAN

Mak: Pass the pepperoni please.
Fazor: "Hail, Bautainia! We pledge our hearts to thee! Science and woo, some babbling too, and astron-oh-meee!"
slang: And it made ash out of yew and tree.
Nicolas: ......you get somebody to yell "two engines, moron" at you... :D

See also please the thread by Mr RickJ, you know, in the astrphotography section...about Arps....He has very kindly posted a beautiful composition of his, Arp 227...here:
Arp 227 a shell galaxy

It is exquisite. And his great explanation and background info. Thank you Mr J.

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clear skies

If you want to make an apple pie from scratch, you must first create the universe. CARL SAGAN

Mak: Pass the pepperoni please.
Fazor: "Hail, Bautainia! We pledge our hearts to thee! Science and woo, some babbling too, and astron-oh-meee!"
slang: And it made ash out of yew and tree.
Nicolas: ......you get somebody to yell "two engines, moron" at you... :D

Hey MAPNUT....

with my, not terribly concentrated search, here at BAUT...I came across 278 threads on Galaxy Collisions / Mergers, if you prefer...

I haven't found the original one, referred to, in my post above. But hey, looking around, BAUT, it's a treasure trove of such exciting stuff.....

Just a casual peek back...I came across this one, started by Antoniseb, in August 2006.
and which leads to post at #06 by Tim Thompson. This includes some exciting links, you may like to explore.
I would call them I hope this helps sate your curiousity a little. I am not at my home terminal, so can't access my library files.
I like this one: http://burro.astr.cwru.edu/JavaLab/G...hWeb/main.html
Thank you, Mr Thompson...excellent link.

I love BAUT people.

edit:
A succinct, beautifully optimistic comment at OP!...

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clear skies

If you want to make an apple pie from scratch, you must first create the universe. CARL SAGAN

Mak: Pass the pepperoni please.
Fazor: "Hail, Bautainia! We pledge our hearts to thee! Science and woo, some babbling too, and astron-oh-meee!"
slang: And it made ash out of yew and tree.
Nicolas: ......you get somebody to yell "two engines, moron" at you... :D

Yep, however much I meditate on the emptiness of space within a galaxy I still struggle to imagine a field of a 100 billion stars merging with another without the odd bump.

Perhaps the key is to recall how big and voluminous galaxies are: if one were a plate in front of you another might be a plate on just the other side of the room (compare with stars where the other plate would be in the next county).

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Yonder is Dubhe seen on Earth tonight as it was in the days of Grover Cleveland's presidency whereas this way is Deneb seen as it was in the lifetime of Muhammed . If one somehow travelled to Deneb at very close to c then whenever you looked back you'd measure Earth as closer to you than the distance you would simultaneously measure between Earth and Dubhe.