Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2002 November 11 The Outer Shells of Centaurus A Credit: 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? Last month 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. Another interesting feature of Cen...