Arp’s Peculiar Galaxies
Page 9 of 11
Arp observations 81-90 of 110 total to date.
| Thumbnail | Title/link | Arp Category | Date Observed | Observer Description |
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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 suggests the galaxy is breaking apart. Yet Arp's remarks suggest, "Considerable resolution into stars and absorption tubes", Absorption tubes I can somewhat understand. There do seem to be dark veins running along the surface. They're more clear in Arp's (Oh, what I would give for a 200" telescope and clear mountain air"), but you can see corresponding veins in my capture. But fission? I don't see anything here that suggests fission. Indeed, current consensus is that this is an area of active star-birthing. See: https://esahubble.org/images/potw1243a/ |
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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 nuclei 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 believed in galactic fission... but it runs totally against mainstream cosmology. Mergers seem like such a simpler explanation, and Occam's Razor applies in my mind. I certainly think that incomplete fusion is the simpler explanation of the appearance here. I did give Arp the benefit of the dark here. To my mind the plate is overexposed, so I worked on it and "developed" a positive image to see if there was something I was missing. Arp does call out the "faint outer oval" in his notes, and I tried to enhance the positive view of the plate to provide a balanced appearance. I did notice two, low surface brightness companions, close by, SW of the disk. Does that change the argument? Not in my mind. |
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Arp 242 / NGC 4676 / Mice Galaxies | Galaxies with the appearance of fission | 2025-03-26 01:00:00 | We're seeing two small spiral galaxies approaching a merger. The "tails" are tidal tails... the closer ends of the galaxies experience much greater gravitational attraction than the far ends. As the galaxies move towards each other, the far ends leave behind some stars. Arp didn't believe in galaxy mergers which seems strange today. He notes "Very thin, bright tail from north nucleus which has strong absorption," but categorized the peculiarity as the "appearance of fission". How two perfectly formed spiral galaxies could be established from a "fission" seems so much more complicated than the modern consensus that galaxy mergers are commonplace. Arp was observing phenomena which few other astronomers were paying attention to -- indeed he was paddling upstream against the orthodoxy that was trying to identify regularities, not peculiarity. Bottom line, in this case, I think his "fission" idea is dead wrong. But given the state of knowledge at the time, the phenomena were worth pointing out even if the implied explanation was incorrect. A fun capture on a clear night with crummy seeing as evidenced by every visible object twinkling noticeably. |
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Arp 244 / Antennae Galaxies | Galaxies with the appearance of fission | 2024-05-02 22:17:00 | This is an entertaining target showing two bright galaxies in an intimate embrace, with a long narrow filament extending behind, and appearing to terminate at a tiny dwarf galaxy. The filaments are quite evident in the color image; if you can't see them, please boost the brightness on your monitor and zoom into the image. Fission or merger I suppose are symmetrical notions, so one can draw either conclusion from the heavily distorted structures; 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". I remain skeptical though admire his contrarian spirit. |
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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". His remarks add, "Some resolution into knots." Both statements are true enough: on the N (top) end it does resolve into knots. It's all a bit surrealistic, like Salvador Dali's clock in The Persistence of Time. While I don't understand the details, Arp was personally invested in the idea that galaxies didn't merge in order to explain interactions he perceived between galaxies of different red shifts. From the little I've read, the argument swung on the "probabilities" of distant galaxies aligning visually by chance. This strikes me as deeply flawed, since there's a selection bias working in the other direction: it's particularly odd in cases like this observation where the visual evidence of merger seems so compelling. In the middle, there's a nearly intact spiral. At the S end, a high-brightness spiral dwarf appears to be in the process of merging, moving in at a more extreme NE to SE tilt. The bend in the middle is a reaction to the relative motion. |
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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 (NGC 4490), the other small and spiral (NGC 4485). In the gallery you'll find a second observation made using the same EdgeHD telescope, but with the 0.7x reducer and the Apollo M-mini mono camera. 44m of integration time. It does a better job of revealing the halos surrounding both galaxies, especially in the inverted view. I'm guessing that this is caused by new star formation stimulated by the interaction. This is not based on research, but observing similar phenomena in other Arp galaxies that astronomers interpreted that way. |
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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 is not one of those examples. |
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Arp 271 / NGC 5426 / NGC 5427 | Galaxies with connected arms | 2024-05-13 01:55:00 | Captured at the end of a long evening. I'd been focused on Messier objects due to so-so transparency, but decided it had cleared up enough at 1:30 AM. Wonderful, relatively bright observation showing two spiral galaxies heavily interacting. Whether it's a future merger or a near miss is beyond my expertise, but the exchange is clearly visible. Arp remarked: "Arms linked. Note bifurcation in arm of N spiral." I believe Arp is describing the bottom arm of NGC 5427 which is rooted in another arm rather than in the nucleus. There is actually faint glow at the point of intersection. I'm tempted to speculate but won't. |
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Arp 273 | Galaxies with connected arms | 2024-11-05 20:51:00 | This is a very mysterious duo of galaxies. The smaller, to the left, appears like a ribbon because it has been largely stripped of its envelope of stars. The larger, right, is a weirdly distorted, barred spiral, in 3/4 view. To be clear, the bright object in the center is actually a star, not the galactic nucleus. The actual nucleus is just above it, and therefore asymmetrically located within the spiral. The top arm has been pulled left. The bottom half of the spiral is partially stripped and what remains is heavily knotted: this is less obvious in my capture, but very clear in Arp's. I see that some sources explain the mystery by the smaller galaxy having actually passed through the larger. This is certainly consistent with what i can see, particularly in Arp's capture, which I "printed" as a positive image because I felt it showed the chaos better. |