Arp 18 / NGC 4088

Designation(s)Arp 18, NGC 4088
Object Type(s)Galaxy
Relevant Catalog(s)All (Chron), Arp, NGC
Arp CategorySpiral galaxies with detached segments
Obs. Lat/Long42° 17', 073° 57'
ConstellationUrsa Major
Date and Time Observed2024-04-16 22:33:00
InstrumentEdgeHD 8" f10-2,032mm FL
CameraASI294mc-Pro
Image DetailsUp is 275.1 degrees E of N. Total integration time was 40m 30s. Exposures 30s@305g, UV/IR Cut Filter. Darks subtracted, no flats. Dithered and recentered in SharpCap. No guiding..
DescriptionArp categorizes this as a Spiral Galaxy with detached segments, which is apt if not particularly evocative. Clearly the center of the galaxy exhibits a distinct spiral structure. I appreciate that Arp himself rejected the idea that peculiar galaxies were the result of mergers, but this certainly looks like a candidate for one. The segments above the spiral could be a second galaxy, partially merged, which we are viewing edge-on. It's gull wing shape could be the the center of the original, separate, galaxtic plane being attracted more quickly than the periphery. If the merger approached from the lower right and then swung around counter clockwise to its current position, it could help explain the lower detached arm.
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