Both the SKA and CTAO are large, multinational science projects, operated and funded by consortiums of research bodies from many countries. Both have designs that exceed the limits of currently available technology, and will spur research and innovation in the fields of engineering and computing. But while both will also set new records in power and sensitivity, they are limited in what sorts of radiation they can detect. SKA will operate in radio bands, from 50 MHz to 30 GHz, while CTAO will detect high-energy gamma rays, on the opposite end of the spectrum. In recent years, multi-wavelength astronomy has become increasingly important, as it allows astronomers to know what’s happening in an observation at all energy levels, from radio to visible light to Xray. Since no single telescope can see the entire spectrum, agreements like the one signed by SKAO and CTOA are vital for future scientific research.
The CTAO is a network of gamma-ray telescopes, spanning two continents. The Northern site is on La Palma, in the Canary Islands, while the southern hemisphere site will be built near Paranal, in Chile. Each site contains an array of different sized Cherenkov telescopes, similar to those at the High Energy Stereoscopic System (HESS) observatory in Namibia.
Gamma rays emitted by high energy sources across the Universe cannot be directly detected from the surface of the Earth, as they interact with air molecules in the upper atmosphere. In doing so, however, they create cascades of new particles which emit a very brief flash of light, known as Cherenkov Radiation. Cherenkov telescopes are equipped with extremely sensitive high-speed cameras which can detect these flashes. This allows scientists to not only indirectly detect gamma rays but also to measure their direction and energy.
When it is completed, the SKA will be the world’s largest and most powerful radio telescope. Like CTAO, it is divided between two sites, both consisting of large arrays of detectors, spread out across the landscape for maximum sensitivity and resolving power. The Australian site, centred on the Australian Square Kilometer Array Pathfinder (ASKAP), will eventually host over a million low-frequency antennae. The Southern African site, centred on the MeerKAT array in South Africa, will extend out to an area spanning 3000 km.
Allen Versfeld is a science writer, an amateur astronomer and a consulting cloud technologist. He has been writing on space and astronomy since 2009, and is the host and producer of the Urban Astronomer Podcast. Allen lives in a major South African city, where he likes to complain about the steady increase in light pollution.