| Designation(s) | Arp 18, NGC 4088 |
| Object Type(s) | Galaxy |
| Relevant Catalog(s) | All (Chron), Arp, NGC |
| Arp Category | Spiral galaxies with detached segments |
| Obs. Lat/Long | 42° 17', 073° 57' |
| Constellation | Ursa Major |
| Date and Time Observed | 2024-04-16 22:33:00 |
| Instrument | EdgeHD 8" f10-2,032mm FL |
| Camera | ASI294mc-Pro |
| Image Details | Up is 268.7 degrees E of N (West). Total integration time was 40m 30s. Exposures 30s@305g, UV/IR Cut Filter. Darks subtracted, no flats. Dithered and recentered in SharpCap. No guiding.. |
| Description | This appears to be a heavily distorted, formerly barred spiral galaxy. There are two "detached segments" that could account for Arp's categorization. The first is the stretched arm to the eastern (lower) end of the disc. This appears to be a former spiral arm, that was shifted by a gravitational encounter of some kind. The second is the arm sticking out from the western (top) end of the galaxy. This appears to be a partially digested dwarf galaxy merger. It could also account for the lower arm's detachment if it (the dwarf galaxy) approached from the East (bottom), passed westward to detach the spiral arm, then swung back to collide with the main galaxy after gravity attracted it sufficiently to begin a merger. |
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