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. 2013 May 14 Galaxy Collisions: Simulation vs Observations Images Credit: NASA, ESA; Visualization: Frank Summers (STScI); Simulation: Chris Mihos (CWRU) & Lars Hernquist (Harvard). Explanation: Wha..