SCIENTISTS HAVE KNOWN ABOUT COSMIC RAYS FOR A CENTURY. But these high-energy subatomic particles, which stream through space at nearly the speed of light and crash into the Earth’s upper atmosphere, have been mostly a mystery. The primary reason: researchers have been unable to tell where they come from, or how they’re born.
Using data from NASA’s Fermi Gamma-ray Space Telescope, the research team led by Dr. Stefan Funk of KIPAC was able to track gamma rays – the most energetic form of electromagnetic radiation, or light – back to the remnants of supernovae explosions where they were born as decay products of collisions between cosmic rays and lower energy particles. The finding offers the first astrophysical evidence for how cosmic rays are produced, as well as where they are generated: in the shock waves that emanate from an exploded star.
Science writer Bruce Lieberman asked your questions about the new data on cosmic rays in an interview with Stefan Funk, Assistant Professor of Physics, Stanford University, and member, KIPAC.
About the Participants
STEFAN FUNK is an Assistant Professor of Physics, Stanford University, and member, KIPAC. 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.
BRUCE LIEBERMAN is a freelance journalist with more than 20 years of experience in the news business. He worked as a reporter at daily newspapers for many years before becoming an independent writer and editor in 2010. For The Kavli Foundation, Bruce has interviewed researchers about galaxy clusters, dark matter and dark energy, string theory, the emergence of the first stars and galaxies, exoplanets and other subjects. He has also written for Scientific American, Smithsonian Air & Space magazine, and Nature about a variety of science topics.