Italy has formalized the proposal to build the Einstein Telescope (ET) in Sardinia, in the Nuorese area, a pioneering third-generation observatory for gravitational waves which will make a decisive contribution to improving our knowledge of the universe and its physical processes that govern it. Italy leads the group of nations that presented the proposal as part of the 2021 update of the ESFRI roadmap, the strategic European forum that defines what the future large research infrastructures will be in Europe, by virtue of its long scientific tradition in the field of direct detection of gravitational waves. The commitment undertaken by the Italian Ministry of University and Research to host this infrastructure in Sardinia is supported by expressions of interest from three Italian national research bodies: the National Institute of Nuclear Physics (INFN, coordinator of the project together with the Dutch Nikhef, National Institute of Subatomic Physics), the National Institute of Astrophysics (INAF) and the National Institute of Geophysics and Volcanology (INGV). The Sardinia region, as well as the universities of Sassari and Cagliari have expressed their keen interest in installing this advanced research infrastructure.
“Large research infrastructures are a driving force for scientific, technological and economic growth”, underlines Antonio Zoccoli, president of INFN. “Hosting large research infrastructures – continues Zoccoli – means attracting top-level young researchers and scientists from all over the world to one's country, it means encouraging the development of a high-tech industrial fabric, it means conquering an international leadership in the scientific field”. "Being able to carry out these ambitious projects in Italy would represent a unique opportunity to catalyze the influx of new resources into our territory, in terms of both scientific and technological skills and economics, strengthening the excellence of Italian research in these areas, and encouraging the innovation and competitiveness of national industry on the global market”, concludes the president of INFN.
“ET will allow scientists to reveal coalescence events of two medium-mass black holes in the entire universe, contributing to the understanding of its evolution - explains Michele Punturo, international project manager - and will allow us to see the dark universe in a new light, clarifying what roles do energy and dark matter play in the structure of the universe”. ET will explore the physics of black holes in detail. These celestial bodies, characterized by a gravitational field of extreme intensity and whose existence is predicted by Albert Einstein's general relativity, but for this reason they are also the place to try to observe phenomena not predictable by this theory, opening new chapters of Physics. ET will detect thousands of binary neutron star coalescence events per year, improving our understanding of the behavior of matter under extreme conditions of density and pressure, impossible to reproduce in any laboratory. In addition, we may have the opportunity to study the nuclear physics that dominate supernova explosions.
“This is a very ambitious project, which opens up follow-up prospects in the electromagnetic spectrum at all wavelengths, in which INAF, with its advanced ground-based infrastructure and its involvement in prestigious space missions, will give a contribution of historic importance” says Nichi D'Amico, President of INAF and Full Professor in Cagliari. “The project - continues D'Amico - sees Sardinia as the host territory, a region that has already given proof of its determination in facilitating and supporting the establishment of our scientific infrastructures on the island; the University of Cagliari is already involved in avant-garde projects of modern astrophysics, and possesses internal expertise in physics and engineering, which are fully reflected in the scientific and technological issues that represent a real challenge in the Einstein Telescope. The initiative - concludes D'Amico - sees scientific and academic institutions not only of high profile, but already rooted in a territory that shows an evident willingness to invest in science and culture".
ET will be installed in a new infrastructure and will use very advanced and innovative technologies and will make it at least ten times more sensitive in detecting gravitational waves than current instruments, the second generation Advanced Virgo interferometers for gravitational waves, located in Italy, all the EGO European Gravitational Observatory managed by INFN and the French CNRS, and the two LIGOs in the United States. Because of this, ET will play a unique and fundamental role in the field of multi-messenger astronomy. The exceptional discovery of August 17, 2017, with the observation of gravitational waves and electromagnetic radiation emitted by the same source, opened a window on this new scientific field that will be fully explored by ET together with the new generation of telescopes for the detection of electromagnetic waves from the ground and from space in which INAF is directly involved, such as ELT, SKA, CTA, Vera Rubin Telescope, ATHENA, THESEUS, to name a few.
To operate to the best of its potential, the ET observatory will have to be built in a geologically stable and sparsely inhabited area; ground vibrations of both artificial (vehicle traffic, industrial activities) and natural (earthquakes) origins can in fact mask the weak signal generated by the passage of a gravitational wave. Since March 2019, INGV has installed, in collaboration with INFN and Sapienza - University of Rome, some seismic stations at the disused mine of Sos Enattos (in the municipality of Lula, in the province of Nuoro) which could host one of the top future observatory. The first results, which are being published in the journal "Seismological Research Letters", indicate that Sos Enattos is characterized by extremely low seismic noise, so much so that it ranks among the 50 "quietest" installations in the world.
"INGV is contributing to the choice of the most suitable area for the infrastructure which will also represent a great opportunity to measure the functioning of the Earth, its continuous oscillations, its internal structure, the astronomical effects that deform it daily" stated Carlo Doglioni and Gilberto Saccorotti, respectively president and director of INGV.
The new gravitational detector is a unique development opportunity of its kind: it is an infrastructural investment of at least one and a half billion euros. Under construction it will bring work to more than 2500 people in a sparsely populated area; in the long term it will be a great scientific pole of international value, destined to attract new resources to invest at the frontier of new science and technology, an engine of development and cultural growth for Sardinia and for the whole of Europe.
“The involvement of the University of Cagliari is a new demonstration of the policies that the University of Cagliari pursues – declares the Rector Maria Del Zompo – Culture is the basis of innovation, which in turn is the foundation of economic growth. The excellence present in the University of Cagliari in the fields of physics, mining, energy and electronics engineering, information technology, geology and telecommunications make the University's contribution not only of knowledge, but also of competence, and will be an outlet natural for our students, PhD students and researchers, helping to strengthen the Italian candidacy. Innovation is the result of a process in which knowledge increases in value over time based on the discoveries of the past which become the basis of future knowledge: the example is the mines. Being able to use a reality from Sardinia's past as a basis for the development of the future demonstrates the importance of university culture, because the foundations of those who build on the past are more solid than those who limit themselves only to the present, even in projects like this one than in years will surpass the current state of the art”.
“ET is a scientific and technological enterprise of global importance, and I therefore express all my satisfaction with this first milestone, which was possible to achieve thanks in the first place to the commitment of the University of Sassari, INFN and all the scientific bodies involved” comments the Rector of the University of Sassari Massimo Carpinelli. “Now we hope that our great project will be included in the next ESFRI Roadmap and that it can be hosted in Sardinia. The presence of a first-rate research center in Sardinian territory opens up prospects of exceptional importance for the development of the Region and for the future of all young Sardinians”, concludes Carpinelli.
The second site under evaluation for the construction of the ET infrastructure is the Euregio Meuse-Rhine, on the borders of Belgium, Germany and the Netherlands. The decision on the future location of ET will be made within the next 5 years.
Artist's impression of the future Einstein Telescope. Credits: ET steering committee