Arp’s Peculiar Galaxies
Page 8 of 10
Arp observations 71-80 of 99 total to date.
| Thumbnail | Title/link | Arp Category | Date Observed | Observer Description |
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Arp 225 / NGC 2655 | Galaxies with amorphous spiral arms | 2024-02-29 00:00:45 | Amorphous spiral arms indeed! During capture they were just perceptible on my SharpCap live stack, which means that post-processing was required to make them visible in the final web images. The core and central disk are quite evident, but the arms are diaphanous. If they contained more stars this would look like the Pinwheel Galaxy! |
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Arp 229 / NGC 507-508 | Galaxies with concentric rings | 2024-12-26 19:39:00 | NGC 507 is a large and relatively bright galaxy where the galactic disc forms discrete rings of diminishing brightness as you move away from the core. This is categorized as a lenticular galaxy: more structure than a typical elliptical galaxy, but lacking the arm structure for a spiral. If you examine all of the galaxies so categorized in the Atlas (227-231), the first three (227-229) all depict a pair of galaxies, with a large, central lenticular galaxy. Confusingly, the other two (230-31) depict polar ring structures within a single, lenticular framework. |
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Arp 233 | Galaxies with the appearance of fission | 2024-02-21 00:00:35 | This is a tiny object which stresses the limits of my 8" SCT with 294 sensor. The featured image reproduced here is only 158 pixels in the original capture where it appears as an elongated blob. Given that Arp described this as a galaxy "with the appearance of fission", I processed the SharpCap .png in Affinity Photo to emphasize the asymmetry within the capture. After processing, a slight elongation at approximately 190 degrees relative-rotation is more evident. Nevertheless, of the 23 Arp Galaxies so categorized (Arp 233-256), this is the most "normal" looking and least obvious fissioning galaxy in the series, even with the benefit of the 200" Hale Telescope's resolution. |
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Arp 234 / NGC 3738 | Galaxies with the appearance of fission | 2025-01-03 22:37:00 | Because of its irregularity, this is a very challenging object to interpret. "The appearance of fission" presumably refers to the two lobes at the top (west side) of the target, flanking a line that bisects the bright central disk until close to the center. There's a second line that runs nearly parallel close to the southern flank of the galaxy. But why interpret them as fission rather than fusion? The standard negative plate in the atlas provided little help, so I "developed" it Affinity Photo and provide it in the comparison image. Although there's much higher resolution from the 200" Hale Telescope than my EdgeHD, I don't see anything in Arp's image to reduce my confusion. |
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Arp 235 / NGC 14 | Galaxies with the appearance of fission | 2024-10-26 22:22:00 | This is a puzzling galaxy with what looks like at least 2, and possibly 3, elliptical galactic centers at slightly different orientations. The result is a galaxy with a much larger and more elongated, irregular center than normal. Arp categorizes this as having "the appearance of fission", and I suppose that's possible if you thought that there exists a mechanism for fission. Arp was not a fan of galactic merging... but I certainly think that incomplete fusion is the more likely explanation of the appearance here, given that gravity is a simple mechanism, and that mergers are now a broadly accepted mechanism for galactic evolution. |
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Arp 244 / Antennae Galaxies | Galaxies with the appearance of fission | 2024-05-02 22:17:00 | First observation of the night, on an evening when it wasn't forecast to be clear at all. Turned out to be clear enough, though we struggled with some high clouds. We'd decided to capture 30 minutes, but cut things short by 30s when the brightness filter on SharpCap rejected the last 5 lights. The dust lanes which appear to show ejecta from each of the two galaxies are quite evident; if you can't see them, please boost the brightness on your monitor. This does appear to show two galaxies in a well-advanced merger: the original spiral structures are heavily distorted; somewhat evident in NGC 4038 (right), and largely destroyed in 4039. While the notion of a merger is well accepted now, Arp usually interpreted galaxies as breaking apart or ejecting matter. Hence his categorization of these "with the appearance of fission". |
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Arp 262 / UGC 12856 | Galaxies with irregular clumps | 2024-10-28 22:53:00 | Arp classified this object into "Galaxies with Irregular Clumps". True enough, it is clumpy, but the consensus now appears to be that we're seeing a small galaxy absorbing a dwarf galaxy (bright clump on the right. Again, conventional thinking in the 1960s was that galaxies didn't merge because the distances where thought to be too great... But when I look at many Arp objects they seem to show mergers, and this is certainly one of them. |
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Arp 268 / Holmberg II / UGC 4305 | Galaxies with irregular clumps | 2024-03-26 00:01:45 | This appears to be an irregular dwarf galaxy with low surface brightness, and a series of small structures above the surface. They remind me of structures I've seen in other contexts, similar to NGC 604 outside of the Triangulum Galaxy, or even M42 within our own galaxy. Certainly they could be star birthing regions. Considering this was a full moon, I was pleased with this capture in SharpCap. |
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Arp 269 / Cocoon Galaxy | Galaxies with connected arms | 2024-02-19 17:55:00 | This is just a fun EAA object. Relatively large with lots of detail. Loved capturing it! The connected arms appear to have been separate galaxies at one point... one large and distorted, the other small and spiral. |
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Arp 270 / NGC 3395-6 | Galaxies with connected arms | 2024-05-31 22:54:00 | Two strongly interacting galaxies, both spiral originally and now significantly distorted by the interaction. There is a tiny and very faint galaxy, IC 2605 which appears to extend the right arm of NGC 3395, the upper galaxy in our image. It's not at all obvious, but showed up in the Astrometry annotation. It has a higher redshift than the two larger galaxies, and is apparently far in the background. Arp famously argued that galaxies with different red shifts could interact, but this apparently not one of those examples. |