Cherenkov Telescope Array. Illustration showing part of the Cherenkov Telescope Array (CTA) planned for the southern hemisphere at the European Southern Observatory's Paranal Observatory in Chile. These Imaging Atmospheric Cherenkov telescopes (IACTs) are used to detect high-energy gamma rays by detecting the particles produced as the gamma rays impact the Earth's atmosphere. The array will be used to study active galactic nuclei, star-forming systems and other phenomena, as well as searching for dark matter particles and deviations from Einstein's theory of special relativity.