While working on getting some of the bugs out of my system after a very long layoff due to typical western Oregon winter weather, an unexpected clear slot opened that left me scrambling for targets to image. I was inspired by @Yizhou Zhang 's fine image of this same field of view, which closely matched what I can see. The plus was its favorable position in the sky at this date and the fact that I had a chance to capture a few very interesting and beautiful galaxies but also a planetary nebula. There are very few PN that make sense for a RASA. This one is large. I was not sure that I would be able to capture both the galaxies and the PN in OSC. I am happy that I tried this.

Galaxies NGC 4725 and 4747 are closely space such that they are gravitationally interacting. Clearly the impact is much more profound with 4747, the much smaller of the two. There are two stellar streams being ejected far from the core of 4747 that are visible. No doubt 4725 is also impacted and this may explain the interesting features it possesses. I find NGC 4725 to be both beautiful and fascinating. As it is thought that normal galaxy evolution is to transition spiral galaxies eventually to elliptical in form (possibly through a transitionally lenticular phase), 4725 appears to possess qualities of both. A distinctive ring surrounds a lenticular/elliptical-like core (which is claimed to be a double bar rotating in opposite directions) at some distance from the center with a very distinctive transition. Outside of this, a single strong spiral arm emanates. This ring and arm resembles many others found in spiral galaxies, with many blue star-forming clusters and dark complex molecular clouds. So two galaxies in one! This is interesting, because the movement of material in spiral galaxies (generally in bulk, not individual stars) is for the material to revolve around the center of the galaxy, almost as if these stars and gas clouds are orbiting the center as in a planetary system with a gravitationally dominant star in the center. We now "know" that the sizes of galaxy cores (yes even with super massive BHs) cannot exert such forces over such distances and that it is dark matter that drives this process. However, elliptical galaxies don't work that way. Unlike spiral galaxies, the stars in ellipticals follow random paths and do not rotate. This is similar too star movement in globular clusters. And the gases and molecular clouds are more randomly and evenly distributed with little new star formation. I wonder how these two different processes can exist within one galaxy, presumably driven by dark matter that controls both strong rotation in the outside, while there is much less rotation in the center? I believe that we can see some evidence of this dichotomy in my image if you zoom in. (However, find an image from a larger telescope on line for an even clearer view!) Unlike most ellipticals, one can see that there are in fact streams of molecular clouds that penetrate the inner portion of 4725 deeply into the core. While these clouds, as they reside in the ring, are parallel to the spiral arms in the outer galaxy and going with the tangential flow, they appear to be falling into the center and eventually seem to fall almost straight in, becoming random near the center. To me this is striking and almost direct evidence for the difference in these two aspects of galaxy structure/dynamics. But they also appear to challenge my simple understanding of how a large halo of dark matter can drive such actions. After all, does it not appear that these clouds are reaching and falling in toward the center? Would that not be gravity driving that? How does dark matter in a halo do that?

The PN is unique in that it is one of the largest we know. Certainly it is large in this field of view! It also is the one closest to the galactic north pole and at its distance is removed from the galaxy plane enough that its expanding shell of ionized gases expands into a relatively low density intergalactic medium. If it were in a denser location, perhaps we would see a more colorful display. I was worried that my OSC would not see this, since it emits almost exclusively from doubly ionized oxygen. The progenitor star is one of the hottest known at 150,000K and is known to be part of a double star system. This may be the reason that this PN is double-lobed, however we see it nearly end on.

Finally, this area also contains many small galaxies that are likely very distant (typically appear as small red smudges) and likely red-shifted. There is a particularly large dense region of these to the left of the PN. I am not sure that it will be visible in the jpg that I present here, but it has an interesting filamentary structure, with denser foci. Not sure how to get more info on these and the structure. These have also been seen and mentioned by others on AstroBin.