Cartwheel Galaxy in Sculptor
The Cartwheel Galaxy (also known as ESO 350-40) is a lenticular and ring galaxy about 500 million light-years away in the constellation Sculptor. It is estimated 150,000 light-years across. The galaxy apparently underwent a head-on collision with a smaller companion approximately 200 million years before. The shock wave swept up gas and dust, creating a starburst around the galaxy's center. This explains the bluish ring around the center. It can be seen that the galaxy is beginning to retake the form of a normal spiral galaxy, with arms.
Find an image taken with the Hubble telescope here: http://hubblesite.org/newscenter/archive/releases/1995/02/image/b/
LRGB (L 21x20m, R 8x20m, G 8x20m, B 8x20m) total 15 h combined. Seeing 0.7-1 arcsec;
Processing: Johannes Schedler
80cm f/7 Astrooptik Keller corrected cassegrain, FLI Proline 16803, Baader Filters, Prompt 7 CTIO Chile
Full field in 25/100% below (North is down)
Here a central crop in 75/150% size: