November 26, 1996: Analysis of dramatic Hubble telescope images reveals immense comet-shaped knots of gas in the heart of the Cartwheel Galaxy. The galaxy's unusual wagon-wheel shape was created by a nearly head-on collision with a smaller galaxy about 200 million years ago.
The discovery of the knots may eventually help answer some compelling questions, such as why the center of the Cartwheel has little star formation and what causes the unusual spoke-shaped pattern between the bright outer ring of young stars and the mysterious, dusty galactic center. The galaxy's center is the bright object in the center of the left-hand picture; the spoke-like structures are wisps of material connecting the core to the outer ring of young stars. The close-up image of the galaxy's nucleus [picture on right] reveals the comet-like knots of gas. These knots are mostly confined to the core's left side and appear as white streaks inside the blue ring.See the rest:
Credit: Curt Struck and Philip Appleton (Iowa State University), Kirk Borne (Hughes STX Corporation), and Ray Lucas (Space Telescope Science Institute), and NASA