In this segment of our "How far away is it" video book, we cover interacting or colliding galaxies.
We begin with the trajectory of Andromeda with respect to our Milky Way. They are on a collision course. We describe what it means for galaxies to collide given the great distances between stars within each galaxy.
We then take a look at some of the interacting galaxies photographed by the Hubble Telescope. These include: NGC 2207 with IC 2163; Apr 256; NGC 6240; the Tadpole Galaxy; UCG 1810 with UCG 1813; The Mice; the spectacular APR 147; NGC 454; and peculiar galaxy NGC 7603 with its multiple red-shift objects;
Next, we discuss how we go about seeing a process that takes a billion years by observing interactions at various stages along the process as understood by computer simulations. Here are a few that illustrate the phases of an interaction: the initial approach -- NGC 6786 with LEDA 62867; first contact -- VV 304A with VV 304B; penetration -- Mayall's Object; out the other side -- ESO 77-14; wrap around -- VV 705; merge -- The Owl. We then show the computer simulation of a collision and highlight the above galaxies along the way.
We end with another simulation. This time it's the collision between Andromeda and the Milky Way.