613 Gamma-ray observations at very-high energies

In the early 20th century, Victor Franz Hess conducted a series of balloon flights that led to the discovery of cosmic rays – charged particles originating from beyond the Earth. These particles have since been measured with energies up to 1020 eV, indicating an origin associated with the most extreme astrophysical phenomena. However, because they are charged, cosmic rays are deflected by magnetic fields, making it difficult to trace them back to their sources. Gamma rays, produced as secondary products in cosmic-ray interactions, do not suffer from this limitation. As electrically neutral particles, they travel in straight lines and serve as powerful tools to probe the high-energy universe. However, traditional imaging techniques are ineffective for gamma rays, as they cannot be focused using mirrors or lenses. Instead, detection relies on methods from particle physics. At very-high energies, above 0.1 TeV, the most effective approach is to use the Earth's atmosphere as a calorimeter, observing the Cherenkov light produced when gamma rays interact with atmospheric particles. In this Praktikum, students will be introduced to the principles of very-high-energy gamma-ray astronomy and standard data analysis techniques used in the field. They will explore emission characteristics of various classes of gamma-ray sources, investigate the long-term and flaring behavior of blazars, and study how gamma-ray propagation through the Universe informs us about cosmic history. This Praktikum includes hands-on coding and data analysis using Python, where students will gain experience with libraries such as NumPy, Pandas, and Matplotlib, and work within Jupyter Notebooks.