The Science of ASTRI

The Universe is populated by extreme particle accelerators, capable of conveying more than 10²⁰ eV in a single proton. The 𝞬-ray photons they can produce could be used as probes to investigate the laws of Nature at the highest energies.

Gamma-rays allow the in-depth study of the violent Universe, from the remnants of supernova explosions to Galactic and extra-galactic jetted sources up to candidate dark matter particles.

Gamma-ray astrophysics is one of the most recent branches of relativistic astrophysics. It investigates radiation thousands of billions times more energetic than the visible light which cannot directly reach the ground. Once they penetrate the atmosphere, the gamma-ray photons interact and produce a cascade of very energetic secondary particles that move at a speed higher than that of light in the air (although still traveling at a speed lower than that of light in a vacuum). In 1937, the Russian physicist Pavel Cherenkov noticed that this phenomenon produced a bluish luminescence (the Cherenkov radiation), conceptually like the sonic boom that accompanies the overcoming of the speed of sound. Cherenkov, Frank & Tamm were eventually awarded the 1958 Nobel Prize in Physics for “the discovery and the interpretation of the Cherenkov effect”.

The Cherenkov radiation is very short living (a few billionths of a second) and very weak (less than a ten thousandth the dark-sky light) and can only be revealed by large telescopes capable of collecting as much light as possible, equipped with instrumentation extraordinarily fast in recording and extremely sensitive. In fact, the current generation of gamma-ray telescopes began to produce important results when it was understood that the performance of the instruments increased greatly by using multiple telescopes operating simultaneously, as opposed to a single huge telescope.