Caption: "The Advanced Camera for Surveys (ACS), the newest camera on NASA Hubble Space Telescope (HST), has captured a spectacular pair of galaxies engaged in a celestial dance of cat and mouse or, in this case, mouse and mouse. Located 290 million light-years (89 Mpc) away in the constellation Coma Berenices, the interacting galaxies have been nicknamed The Mice (AKA NGC 4676) because of the long tidal tails of stars and gas emanating from each galaxy. The pair will eventually merge into a single galaxy, probably an elliptical galaxy." (Slightly edited).

Features:

1. The galaxy on the right NGC 4676a is an S0 pec, where "pec" stands for peculiar galaxy and "SO" for lenticular galaxy. It seems to seen roughly edge-on.

2. The galaxy on the left NGC 4676b is an SB(s)0/a pec (i.e., either SB0 or SBa with no ring (as the (s) says) and in any case a peculiar galaxy and barred spiral). It seems to seen roughly face-on.

3. The Mice are interacting galaxies. They are also a galaxy merger in action: two into one probably on a time scale of hundreds of millions of years.

4. The result of the merger will probably be an elliptical galaxy or, perhaps, a lenticular galaxy.

5. Actually, the tidal tails do NOT seem that obvious to yours truly's untrained eye.

   The Antennae Galaxies have much more obvious tidal tails.

6. How do interacting galaxies interact?
   1. Primarily through gravity. The stars are affected practically only by gravity. The forces of interstellar medium (ISM) and magnetic fields on the stars are probably very small.

   2. The interstellar mediums of the interacting galaxies do interact through the pressure force and magnetic fields.

   3. Stellar collisions (body-on-body collisions of stars) are negiligible. Probably NOT even two field stars will collide in galaxy collisions (see Wikipedia: Stellar collisions in galaxy collisions).

      But if two globular clusters collide the probability of stellar collisions is higher since globular clusters have very high density of stars. Yours truly does NOT know what that probability is.

      But even if it is highish, stellar collisions are still negligible overall in interacting galaxies.

7. For interacting galaxies explicated, see insert interacting_galaxies.html below (local link / general link: interacting_galaxies.html):
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8. See galaxy videos below (local link / general link: galaxy_videos.html):
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