NGC 908 – A Recent Encounter of the Close Kind? OTA:……………….CDK17
Camera:………….SBIG STXL11002 with AOX and FW8G (0.63 arsec/pxl)
Observatory:…. Heaven’s Mirror, Chile 
EXPOSURES:               
…R……11 x 1200 sec.                                      
…B…...16 x 1200                               
…G……11 x 1200               
…L…….17 x 1800               
Total exposure 22.3 hours
Image Width: 22 arc-minutes;

The long axis of NGC 908 is only 6 arc-minutes
Processed by Alex Woronow (2020) using PixInsight, Topaz, SWT =11.0pt

NGC 908 displays very active star formation and an unusual geometry in its spiral arms. Toward the lower right, two arms appear pulled outward from their normal position and splay further apart as they get further from the galaxy’s core. The starburst activity and distorted geometry suggest that NGC 908 may have had a close encounter with another galaxy sometime in the past—but the culprit remains unidentified.

Another strange feature in NGC 908 is an asymmetric star-forming ring around its nucleus described by Menezes, et al. (2019). They also detect some metallicity differences between the core and ring. These features lead the authors to suggest a “minor” merger event affected NGC 908’s core, probably NGC 908 cannibalized something on the order of a dwarf galaxy.

You have probably noticed something else about this galaxy that some others display, but many do not. The distinct spiral arms become an unorganized fog, and faint tails appear at the extreme left and right of the image at a larger radius. (Such faint tails probably surround the galaxy, but at the apparent edges  of the galaxy, their projected star densities make them more visible.) I venture that these features may arise from gravitation disruption, perhaps one of those postulated in previous paragraphs.

If you like to personify DSOs, NewScientist refers to NGC 908 as a “Tormented” galaxy “suffering from a bent spiral arm.” I hope you have a better day than NGC 908 is having!

Alex Woronow