A major step toward answering this century old question may have just come in from the Auger Observatory project, the world's premier cosmic ray observatory.
That high energy fundamental particles are barreling through the universe has been known for about a century.
Pictured above, an artist illustrates a cosmic ray striking the Earth's atmosphere and creating a shower of secondary particles detectable on the surface.
The image of Centaurus A digitally superposed near the top signifies one such active galaxy from which cosmic rays might originate.
