Arp’s Peculiar Galaxies
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Arp observations 21-30 of 88 total to date.
| Thumbnail | Title/link | Arp Category | Date Observed | Observer Description |
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Arp 78 / NGC 772 | Spiral galaxies with small high surface brightness companions on arms | 2023-01-09 11:11:19 | This is one of my last observations using my Evo 9.25 before it was lost via an accident. Waning crescent moon was not visible during observation. At the time, I had been practicing EAA for less than 60 days. I was excited about seeing this dim object emerge as evidenced by the fact that I stayed on it for 68 minutes. For many years I've owned a favorite paisley tie, and this reminded me of it. Image is L-R reversed due to use of a mirror diagonal in the image train. Corrected for the Arp catalog comparison image only. |
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Arp 80 / NGC 2633 | Spiral galaxies with large high surface brightness companions on arms | 2024-02-26 21:30:03 | This was a very challenging night which cleared late, with a 97% moon. High clouds closed in to end observing much sooner than I would have liked. However, the elongated, barred galaxy structure was evident. |
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Arp 81 / NGC 6621 and 6622 | Spiral galaxies with large high surface brightness companions on arms | 2024-09-02 21:28:00 | Captured on a dark night but where clouds closed in and forced me to shut down early. A pair of interacting spiral galaxies with one (6621) exhibiting a long arm separated from the spiral and connecting to the smaller one (6622). The two certainly appear to be in the process of merging, and I would love to see a simulation of the relative motion which created the long, wrap-around separation of the arm. |
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Arp 84 / Heron Galaxies / NGC 5394-5395 | Spiral galaxies with large high surface brightness companions on arms | 2024-05-31 23:23:00 | Finally a dark, moonless night to observe these galaxies. NGC 5395 is a near classic spiral galaxy only slightly distorted by its interaction with NGC 5394, which is an extreme barred spiral. Lovely. It certainly looks like a merger, or at least a strip of stars by 5395 from 5394, which presumably explains the barred spiral configuraiton. Often we see these galaxies by themselves: not often we get to see the theft in progress. The nickname Heron Galaxies is apt, though I don't see it widely used. Anyway, a fun capture on a dark night. |
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M51 / Arp 85 / Whirlpool Galaxy | Spiral galaxies with large high surface brightness companions on arms | 2024-02-19 15:52:00 | This is a very bright and familiar target, which I've captured successfully two other times. This was one of the clearest evenings of the Winter, and decided to stay on it to achieve "near" astrophotography quality despite using EAA techniques. The two galactic centers and the connecting dust lanes are clearly evident. Just beautiful! We've included two "bonus" observations: first an observation using my EVO 9.25, early in my EAA career. The other on July 15, 2024 on a so-so night using my EdgeHD to capture it using Bin2 on my ASI294 camera over 37m, and processed in Affinity Photo. |
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Arp 86 / NGC 7752 and 7753 | Spiral galaxies with large high surface brightness companions on arms | 2024-09-02 20:28:00 | NGC 7753 is a barred spiral galaxy connected via a large arm/dust lane to a much smaller spiral galaxy classified jointly as Arp 86 in Halton Arp's Atlas of Peculiar Galaxies. M51, which is a famous and much larger/brighter pair of galaxies, is classified as Arp 85 in the same category. It appears that 7753's arm was distended by the gravitational pull of 7752 as it passed by from the upper left to lower right. |
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Arp 91 / NGC 5953/5954 | Spiral galaxies with large high surface brightness companions on arms | 2024-05-23 22:27:00 | Fun to be back observing Arps. These two galaxies are pretty small, but bright enough to capture even during a nearly full moon (luckily pointing to a very different part of the sky). It appears to be two galaxies merging (or at least strongly interacting during a "fly by"). NGC 5954 (left) is an elongated spiral, though it's unclear to me whether it was caused by this interaction or an earlier one. I suspect the latter since the distortion isn't obviously in the direction of its partner. On the other hand, you would need to model it: it's possible it approached from below and is in the process of avoiding merger by passing to the right. NGC 5953 (right) is a nearly featureless elliptical galaxy. It's unclear whether the third, bright object (lower right) is a star or a bright, dwarf galaxy. There's a hint of luminosity that suggests dwarf, but we're at the limits of my telescope and the night's seeing, so I'm not sure. |
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Arp 94 / NGC 3227 | Spiral galaxies with elliptical companions on arms | 2024-03-26 18:15:36 | Last observation on a full moon night before high clouds and reflected moonlight killed observing. Arp 94 appears to show two galaxies in close proximity. NGC 3227 is the much larger partner but has been greatly elongated by the encounter. Obviously, we can't tell why it's so elongated, but I presume 3226 may have nearly escaped, and shed many of its stars while passing, creating the elongated appearance. |
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Arp 99 / NGC 7547, 7549, 7550 | Spiral galaxies with elliptical companions on arms | 2024-10-27 20:50:00 | This is a fascinating cluster which appears to capture 3 galaxies in a dance of attraction. The elliptical galaxy NGC 7550 on the left seems to be dominating. It seems to have unwound the sprial galaxy NGC 7549 (upper right) into an extended S curve, and to be attracting and stretching the more intact spiral galaxy NGC 7547 (probably a circular spiral at first). |
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Arp 101 / UGC 10164-10169 | Spiral galaxies with elliptical companions on arms | 2024-06-13 23:07:00 | The Uppsala General Catalogue of Galaxies (UGC) lists 12,921 galaxies visible from the northern hemisphere, first published in 1973. The fact that the two key galaxies in Arp 101 are listed in UGC (and not NGC or IC) underlines how obscure they are. Neither is in Astrometry.net's annotation system. We flipped our image 90° clockwise to match the orientation in Arp's catalog, which means south is up. The more southerly galaxy UGC 10164 (upper) is the "eliptical" galaxy referred to in Arp's categorization at magnitude 14.7; its spiral companion UGC 10169 is 14.9 (the spiral structure is barely evident in my capture and only slightly more clear in Arps'. The critical features are the bridge between the two galaxies and the extended tail on the spiral 10169, which are substantially fainter yet. Suggesting that the bridge between the two galaxies represents a companion "on the arm" of 10169 seems a bit of a stretch (pun intendend). During the capture in SharpCap my emphasis was on showing these connections and not worrying about the background noise or darkness. I wasn't sure if I'd be successful in capturing them, especially given there was a 50% illuminated moon during the capture. I was pleased with the result. I had to cut this observation short due to high clouds starting to trigger the brightness and FWHM filters in SharpCap. |