Arp’s Peculiar Galaxies
Page 17 of 18
Arp observations 161-170 of 171 total to date.
| Thumbnail | Title/link | Arp Category | Date Observed | Observer Description |
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Arp 316 / NGC 3187 / NGC 3189 / NGC 3193 | Groups of galaxies | 2026-03-04 21:30:00 | This is a small cluster which Arp presumably included because he believed, "Edge-on spiral [NGC 3189] shows signs of interaction" - presumably referring to the lower arm curving towards the elliptical galaxy NGC 3193. This is one of the few images in the Atlas not taken with the 200" Hale Telescope. Instead it's one that Arp took using the 48" Schmidt. Remarkably, it delivers roughly the same FOV as my imaging setup: since my framing wasn't identical to Arp's, it turned out the corners of my image didn't quite cover Arp's, which i had to fill in (luckily blank in Arp's image as well). Today, the Vera Rubin telescope is frequently showing structures connecting neighboring galaxies which were historically thought separate, "connected" only by gravity. Arp was a pioneer in focusing on the faint signs of interaction visible though 1960s telescopes. |
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Arp 317 / M65 / Leo Triplet | Groups of galaxies | 2025-03-03 21:11:00 | Discovered by Messier (#29) on March 1, 1780 who recorded additional details in the entry for M66. Here he notes only: "Nebula discovered in Leo: It is very faint and contains no star." <--> This is one of my favorite targets, a stunningly beautiful group of three spiral galaxies. There are multiple observations here with different orientations. Tech details are for most recent triplet image, featured. M66 appears to be bent slightly by the attraction to M65. Arp seems to agree with me, as he remarks: "Both galaxies on east show signs of interaction." All three galaxies are quite bright, distinctly visible even after 60 seconds of integration. I have attached a "bonus" image which is a SeeStar 50 capture -- my first of the Triplet -- during a very dark and clear morning. This is the best galaxy capture I've achieved with this $500 automated telescope, and demonstrates what it can achieve when conditions are "perfect". I've also added to the gallery a capture from March of 2025, representing my first ever of M65 stand-alone, outside of the Triplet. Captured with my EdgeHD, 0.7x reducer, and Apollo M-Mini mono camera. |
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Arp 319 / Stephans Quintet / NGC 7320 | Groups of galaxies | 2024-11-03 19:32:00 | Arp 319 depicts a fascinating, compact cluster of 5 galaxies, 4 of which exhibit dramatic distortions -- extended arms, "tails", and a "fan" -- due to gravitational attraction. One imagines the center 4 are approaching a mega merger.... I became aware of Stephan's Quintet originally because of my affection for NGC 7331, its proximity to this group, and the fact that one of the galaxies here is likely gravitationally bound to it. You can see a 2023 capture in the gallery which I found disappointing in the context of this effort. I wasn't aware of the distortions, and didn't try to capture them. I returned on this date to try to do a better one using my monochrome Apollo-M Mini. This is also the first time I "developed" the negative plate found in the Atlas of Peculiar Galaxies for comparison. |
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Arp 320 / Copeland Septet | Groups of galaxies | 2024-02-19 00:00:06 | These 14th magnitude galaxies are tiny and challenging in the best conditions; even more so with an 83% illuminated moon. This was early in our process, and obviously we did not give this enough integration time. I do intend to return to this target at some point, and would look to capture at least an hour with the mono camera, which at F/7 instead of f/10, would be the equivalent of 2-3 hours with the 294mc. That might not fully do it justice, but would be a HUGE improvement over what we see here. We've managed to save ourselves from utter embarrassment by converting the color image to black and white where we could push it harder. |
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Arp 322 / Hickson Compact Group 56 | Chains of galaxies | 2025-05-11 23:59:00 | The first observation following a clear day, but with a full moon. As it turned out clear enough. |
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Arp 324 (Abell 2147) | Chains of galaxies | 2025-07-23 23:55:00 | Arp comments: "Diffuse elongation of E[liptical Galaxy]'s along line joining them." This is pretty evident in both Arp's plate (probably from the POSS survey and taken with the 48" Schmidt telescope rather than the 200" Hale). Interesting that Arp is posting a subset of Abell 2147. George Abell was a Ph.D. student at CalTech who created the Abell catalog as part of his Ph.D. thesis relying on the POSS survey for data. This was Zwicky's big project during this time. The survey was published in 6 volumes just prior to the Atlas of Peculiar Galaxies being published. Abell identified several thousand galaxy clusters within the survey, and his list (expanded later to include the southern hemisphere) is well remembered and a frequent target source for amateur astronomers. |
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Arp 327 / NGC 1875 / Hickson 34 | Chains of galaxies | 2025-01-02 20:41:00 | This is a tiny, dim group consisting of four galaxies: the brightest is an elliptical galaxy, NGC1875 (13.7m, 0.8'x0.7'). Then, moving up the chain (and the image): PGC1716 (18.3m, 0.2'x0.2'), PGC17175 (17.1m, 0.4'x0.2'), and PGC17173 (17.4m, 0.4x0.2m). The smaller, dimmer galaxies appear to be younger and spiral. Consistent with the close proximity of the four, filaments connecting them are evident. Arp's comment: "Three distorted galaxies in general line toward east." I agree. One imagines that the ultimate outcome will be that all 3 end up absorbed into NGC1875. Imaged on a windy night that required careful use of SharpCap's brightness and FWHM filtering. I was hoping to capture up to an hour of integration, but clouds closed out observing prematurely. |
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Arp 331 / NGC 383 | Chains of galaxies | 2023-12-06 22:00:06 | This is a very rich galaxy-field. Why Arp included it is a little unclear; his remarks are typically cryptic: "Position of NGC 383. Symmetry around large central galaxy. Velocities known." Besides the galaxy cluster that Arp labels, I counted 12 additional galaxies by eye. The Astrometry.net annotation is so cluttered that it's very challenging to read. Included as part of Arp 331 are NGC 383 (central galaxy), 379, 380, 382, 384, 385, 386, and 388. Additional galaxies within the field of view include: NGC 370, 373, 374, 375, 392, 397, 398, 399, 400, 402, 403 plus IC 1614, 1618, 1619. This means the annotation found at least 2 galaxies I didn't count by eye, presumably the IC galaxies (IC 1614 is 17th magnitude). This observation was part of the December 2023 Cloudy Nights EAA Challenge, which is why I observed it when I did. |
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Arp 333 / NGC 1024 | Miscellaneous galaxies | 2024-12-25 23:23:00 | This is an enigmatic cluster of 3 galaxies, showcased by NGC 1024, although Arp included only NGC 1024 in his Atlas. It's classified as miscellaneous/unique for unknown reasons. His remarks state: "Thin circular arms, star in SE superposed on wisp." I wasn't sure that those objects might not be dwarf galaxies, especially because of the superposition, but it turns out that all of the bright shapes with the comparison image are blown-out field stars. NGC 1029 is likely gravitationally bound to 1024, but 1028 is substantially further away as suggested by its smaller size, and confirmed by a much higher red-shift. But, strictly speaking neither is part of Arp 333. |
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Arp 336 / Helix Galaxy | Miscellaneous galaxies | 2025-03-21 21:49:00 | Arp 336, also know as NGC 2685 and as the Helix Galaxy, is a lenticular polar ring Seyfert Type 2 galaxy in the constellation Ursa Major. Polar-ring galaxies are very rare: it refers to a ring surrounding the galaxy orthogonal to the disc.. They are thought to form when two galaxies gravitationally interact with each other. "The bizarre configuration could be caused by the chance capture of material from one galaxy by a second disk galaxy, with the captured debris strung out in a rotating ring. A Seyfert galaxy is a type of active galaxy characterized by a bright, compact nucleus exhibiting a very hot, energetic region at the center, thought to be powered by a supermassive black hole. <--> There are two observations here: one early in my EAA career (Dec 2022) and the second in March of 2025 (featured). I was about 110 Arp observations into my experience curve in March of '25, and it shows. You see both in the gallery.. March of '25 I was using my 8" EdgeHD with a monochrome camera...this is a rig I'd adopted specifically to capture dim galaxies. December of '22, I'd had less than 30 days of successful captures. Arp was not even a twinkle in my eye. This is a relatively small target which tested the limit of my reduced C9.25 SCT, particularly because I had no idea what I was doing at the time. |