The Outer Shells of Centaurus A . ... Credit Copyright: E. Peng and H. Ford ( JHU ), K. Freeman ( ANU ), R. White ( STScI ), CTIO , NOAO , NSF Explanation: What causes the surrounding shells in peculiar galaxy Cen A? In 2002 a fascinating image of peculiar galaxy Centaurus A was released , processed to highlight a faint blue arc indicating an ongoing collision with a smaller galaxy. ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...