Hunting For Cosmic Rays – With Special Guest Dr. Stephan Funk

August 21, 2013

John P. Millis, PhD for – Your Universe Online

More than a century ago an astronomer named Victor Hess, using a high altitude balloon, noticed that the Earth was getting showered with high-energy charged particles from the Universe. While theories abounded for their possible origin, the following decades were met with more questions than answers.

Eventually, scientists began to believe that these charged particles – known as Cosmic Rays – were probably tied to supernova explosions around the galaxy. But then came the task of proving it.

In this iteration of our podcast series Your Universe Today, I spoke with Stanford University physicist Stephan Funk about the history and questions surrounding Cosmic Rays. And be sure to tune in next time as we talk about his recent work that has seemingly brought closure to this century old mystery.


After receiving his PhD from the Max Planck-Institut fuer Kernphysik and Heidelberg Universitaet, Germany, in 2005, Dr. Funk continued his work on cosmic rays and high-energy astrophysics at the Max Plank Institute, and then later at the Stanford Linear Accelerator and Collider (SLAC). Currently he serves as a professor of physics at Stanford.

Professor Funk’s research focuses on high-energy astrophysics to investigate how particles are accelerated in violent astrophysical sources such as supernova remnants or pulsar wind nebulae. Charged particles arrive at Earth ubiquitously but uniformly from all directions because they are deflected in interstellar and intergalactic magnetic fields. By using gamma-rays – photons a billion times more energetic than visible light – and electrically neutral (and therefore not deflected by magnetic fields), it is possible to test current understanding of the acceleration of charged particles such as protons or electrons in the most energetic objects in our universe.

Professor Funk’s research utilizes data from satellite missions such as the Fermi-LAT instrument as well as from ground-based Cherenkov telescopes, such as the H.E.S.S. telescope system in southern Africa and the planned CTA array.