Good news for gamma-ray astronomy

Last week, the European Commission established the European Research Infrastructure Consortium (ERIC) of the external page Cherenkov Telescope Array (CTAO). The CTAO ERIC was supported by 11 countries, including Switzerland, and by the European Southern Observatory (ESO). The CTAO will be the largest and most powerful gamma-ray astronomy observatory in the world, and the only one to cover the entire sky from Earth thanks to telescope arrays in both hemispheres.

The ERIC is a specific legal form under EU law that facilitates the establishment and operation of research infrastructures with European interest; a European Commission decision is required to set up a new ERIC. In the case of the CTAO, the ERIC provides a formal framework to accept and operate the current telescope prototypes while supporting the immediate start of construction for more than 60 telescopes across both telescope sites. On the CTAO-North site on the Spanish island of La Palma, the Large-Sized Telescope prototype (LST-1) is under commissioning; three additional LSTs and one Medium-Sized Telescope (MST) are expected to be built in the next couple of years to start intermediate array operation by 2028. On the CTAO-South site in Chile's Atacama Desert, the plan is to build the first five Small-Sized Telescopes (SSTs) and two MSTs within a year. These subsets of the final arrays will already be more sensitive than any existing instrument, bringing the Observatory’s early science within close reach.

ETH will be hosting a data center for the CTAO at the external page CSCS Swiss National Supercomputing Centre of ETH Lugano. The participation of Swiss institutions – among which are also the University of Zurich and the University of Geneva – to the CTAO ERIC will be supported by the State Secretariat for Education, Research and Innovation (SERI).

At ETH Zurich, researchers in the Department of Physics have been investigating the highest energetic phenomena in the sky with Cherenkov telescopes for over two decades. The groups of Professors Felicitas Pauss and Adrian Biland were both part of the MAGIC collaboration, which was among the first ones to provide evidence that "the high-energy sky is far more diverse than anybody expected," recalls Biland. That evidence motivated the community to start planning for new-generation telescopes as early as 2006. Biland was a member of the international study group that first laid out the requirements for a new Cherenkov telescope array, including the number and size of the telescopes, the layout of the northern and southern sites, and details of telescope design. Considerable research and development work was carried out at Swiss institutions in those early planning years: Biland's group, for example, successfully prototyped the use of solid-state photosensors.

For researchers like Biland, last week's announcement opens an entirely new chapter of scientific discovery. "With current instruments we found an unexpected diversity of cosmic particle accelerators. With the significantly improved sensitivity of the CTAO, the biggest surprise will be if there are no further surprises," says Biland. Indeed, the CTAO will reach unparalleled accuracy and cover a broad energy range – two features that will help researchers tackle many puzzles in astrophysics. Among the topics that will be investigated thanks to the new Observatory are the origin and role of relativistic cosmic particles, the physics of extreme environments such as black holes and neutron stars, and the search for deviations from Einstein's theory of relativity.