G=EMC^2 Glazier wrote:
What if colliding galaxies need much more thinking? This What if came
out of Cactus Saul posting his answer that stars of a colliding galaxy
just pass each other by without even a hello. Not so fast Saul Im
looking as I type at the Cartwheel galaxy This galaxy has been hit
face on by another galaxy. It created great SHOCKWAVES that spread out
like ripples on a lake.to form a glowing ring of stars at the galaxy
edge. Now we must think what gravity is doing when twogalaxies
collide. Gravity pulls from each galaxy sheets of gas and stars creating
great interaction This is shown to us in these two galaXIES NGC 4038
AND NGC 4039 nEXT TO THE BREATH TAKING PICTURE OF THE cARTWHEEL
GALAXY is galaxy NGC 2207 It is an unbelievable picture. So best
you all see it for yourselves Especially Cactus Saul Bert


The string of commentary following your initial post is one of the
examples I would offer for not spending much time in this group. Very
little science discussion followed.

My comments on what you have posted would have been as follows:

I don't think "shockwave" would be the correct term here, unless you are
talking about shockwaves created from supernova explosions of massive
stars created as gas cloud interacted with gas cloud as the two galaxies
passed through each other.

Gravity obviously plays a role and could, among other things, jettison
stars and gas from either of the two interacting galaxies into the
intergalactic medium. In images of colliding galaxies such as the
Antenna, you can see this kind of thing happening. The Tadpole and the
Mice, pretty images from the HST, also show what can happen after the
galaxies have passed through each other. And computer simulations seem
to reinforce this understanding to the degree that they can result in
computer galaxies similar to the real thing seen by the HST and other
telescopes.

Star-star interactions are likely to be small in probability, but
definitely not zero. Star-star impacts though may be much closer to
zero in probability than the interactions would be, simply because the
interactions would take the form of gravity-gravity interaction of each
star, and not star hitting star.