This is a beautiful shot (super high-res version HERE) of NASA's Ares rocket taken earlier this week just as it broke the sound barrier. Pretty awesome, huh? Just imagine if you were sitting on top. WHEEEEE!!
What you're looking at is called a "shock egg," or the Prandtl-Glauert singularity, or a shockwave that compresses air and forces the vapor out of it. You see this kind of stuff a lot in photographs trailing behind fighter jets, but it's especially awesome when it happens to rockets. According to NASA, the shot was taken by one Scott Andrews, who used a Canon of some sort.
Hell yes, shock egg. Now tell me -- which do you think came first: the supersonic chicken or the shock egg? Trick question! Dinosaurs.