Seeking The Impossible – The Fermi Gamma-Ray Telescope, With Special Guest Dr. Stefan Funk

September 6, 2013

John P. Millis, PhD for – Your Universe Online

I have to confess, I sometimes become frustrated with the amount of time scientists -including my own colleagues – spend on pursuits that seem to have little chance of ever finding success. We point multi-million dollar telescopes at objects that we have almost no hope of detecting, spending valuable observing time and resources.

So why do we do it? The answer is simple: Because the greatest discoveries often come by looking where we expect to find nothing at all.

Not all that long ago astronomers thought the pursuit of designing and building gamma-ray telescopes was a fool’s errand. There couldn’t possibly be natural mechanisms in the Universe that could accelerate particles to such high energy that gamma-rays would be naturally created, at least not at the kind of levels that we would need to detect them from here on Earth.

Not only was that thinking incorrect, but by observing the high-energy (and more recently, the VERY high-energy) Universe we have discovered all sorts of new classes of objects. And even more importantly, these instruments have ultimately worked to change our entire view of the cosmos. The impossible, it seems, was entirely real.

The latest gamma-ray experiment to join the fold is the Fermi Gamma-ray Space Telescope, named for the famed physicist Enrico Fermi. Launched in 2008, this billion-dollar instrument is the most sensitive orbiting gamma-ray satellite ever attempted. And even though the mission is a mere four years in, the results that have already been gathered are changing our understanding of some of the most dynamic objects in the Universe.

Recently, data from the orbiting observatory was used to solve one of the greatest astronomical mysteries of the last century: the course of galactic cosmic rays. To tell us more about the Fermi Gamma-ray Space Telescope and the role it played in this crucial discovery, I was joined once again by Stanford physicist Stephan Funk.

Be sure to listen to the first two parts my interview with Professor Funk, Hunting For Cosmic Rays and Solving The Mystery Of The Origin Of Cosmic Rays.


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.