This object is the famous Leo Triplet of galaxies, located in the constellation of Leo. 

I had previously thought that all 3 of these magnitude 9 galaxies are at the same distance from us, but that is incorrect.  NGC 3628 (at top) and M66 (at lower left) are about the same distance, at 35 million light years, which explains the gravitation interaction that we see in their disks and star streams.   M65 (lower right) is slightly further away at 41 million light years.

NGC 3628, nicknamed the Hamburger Galaxy, is the edge-on spiral galaxy at top. It spans 17 arc-minutes in our apparent view, which corresponds to a diameter of 160,000 light years.  It is rare that a non-Messier object outshines 2 Messier objects in the same frame, but that is the case here because of its beautiful dust lane and 400,000 light year long starstream tail. Its broad equatorial dust band obscures the galaxy’s bright central region and hides most of the bright young stars in its spiral arms. Gravitational interactions with M65 are believed to be responsible for the extended flare and warp of this spiral's disk, as well as the starstream tail. The gravitational pull has most likely tipped the plane of NGC 3628 and made its central dust lane “wobbled” in appearance.  A small satellite dwarf galaxy is seen just below NGC 3628.

I would like to see a simulation to improve my understanding of the formation mechanism of the long tail.  It is puzzling to me why it is so asymmetric, extending so far the left and little to the right.  Also, why aren't the streams between the 2 interacting galaxies more prominent?  One possibility that I have never seen discussed in that NGC 3628 is actually 2 galaxies, one behind the other.  Looking closely at NGC 3628, it is easy for me to imagine that we are looking at one galaxy superimposed in front of an adjacent one, which could then lead to the long tail.  If this sounds far-fetched, take a look at  Arp 190 or  Arp 174 or Arp 242, and imagine if our view perspective of them was slightly different, such that the 2 galaxies of each of those objects were in-line.

M66 is the face-on galaxy at lower left. It has a diameter of 90,000 light years and is oriented about 25 degrees from edge-on in our apparent view.  While all of these galaxies exhibit prominent dust lanes sweeping along their broad spiral arms, M66 is particular interesting in the contrast between the pinkish hues of hydrogen gas in star forming regions and the bluish hues of the young blue star clusters. It also displays a slightly odd non-symmetric structure, likely due to gravitation interaction with NGC 3628. 

M65 is the undisturbed galaxy at lower right. It has a Milky Way like diameter of 120,000 light years and is oriented about 15 degrees from edge-on in our apparent view. I find this galaxy fascinating because of the symmetric brightness undulations as you move from the top of the galaxy to the bottom. The dark lanes appear as six dark circles as you move across the disk, interrupted by the glowing core.

Many other small galaxies are seen in the mouseover.