Conceptual Study for the New Wide Field Spectroscopic Telescope Gets the Green Light

(Image: G. Gausachs/WST)

A €3 million grant has been awarded under Horizon Europe to fund the conceptual study of the Wide Field Spectroscopic Telescope (WST), a new telescope that could become operational in Chile after 2040.

The WST is designed exclusively for wide-field spectroscopic observations in the optical band,  — from distant galaxies to asteroids and comets in our Solar System.

The project is led by Roland Bacon from the Centre National de la Recherche Scientifique (CNRS, France) and Sofia Randich from the Italian National Institute for Astrophysics (INAF, Italy), with contributions from 19 research institutions across Europe and Australia. The scientific team includes more than 600 members from 32 countries worldwide. The University of Bologna is a key participant, represented by its Department of Physics and Astronomy (DIFA).

Professor Andrea Cimatti, Director of the DIFA, stated: “This project represents a considerable strategic investment. Scientifically, the WST is a next-generation telescope for highly innovative research in astrophysics and cosmology. The European funding will allow us to make the WST even more competitive on the future global stage. Politically, being part of this large international team brings great prestige, visibility, and an important network of collaborations to the DIFA and, consequently, to the University of Bologna.”

The consortium leading the project will work on a detailed conceptual study over the next three years, from 2025 to 2027. The goal is to establish the Wide Field Spectroscopic Telescope as the next major observational infrastructure of the European Southern Observatory (ESO), following the completion of the Extremely Large Telescope (ELT), currently under construction in the Chilean Andes.

The study will address all the critical aspects: telescope and instrument design, site selection in Chile for the installation, development of scientific cases, survey planning, operational models for the facility and innovative data reduction and analysis methods to maximise scientific output.

The WST is designed to address a pressing need identified by the international scientific community: a telescope with a 10-metre class primary mirror  dedicated exclusively to spectroscopic observations. This need is outlined in numerous international strategic scientific plans for the next ten years, including the European Astronet Roadmap 2023.

Although several ground-based telescopes with 30-40 metre mirrors are under construction, none of them offers the unique features of the WST: a 12-metre primary mirror, simultaneous operations of a multi-object spectrograph (MOS) capable of observing over a large field-of-view (3 sq. degree, approximately 12 times the size of the full Moon) with high-multiplex capability (20,000 fibres), an integral field spectrograph (IFS) covering an apparent sky area of 9 arcmin2.

Roland Bacon of CNRS explained: “These specifications are extremely ambitious and place the WST project above current and planned observational infrastructures. In just five years, the MOS could capture spectra from 250 million galaxies, 25 million stars at low spectral resolution, and over 2 million stars at high resolution, while the IFS could collect 4 billion spectra, allowing researchers to fully characterise these sources. To compare, the ESO’s VLT IFS would take 43 years to acquire the same 4 billion spectra, while the upcoming 4MOST instrument would need 375 years to observe 250 million galaxies at the same depth.”

Sofia Randich of INAF concluded: “The Wide Field Spectroscopic Telescope will allow researchers to tackle fundamental topics in areas such as cosmology, the formation, evolution, and chemical enrichment of galaxies (including the Milky Way), the origin of stars and planets, the astrophysics of transient or time-variable events, and multi-messenger astrophysics.”

The study will prioritise environmental sustainability, which will be one of the criteria behind technological decisions. Solutions will be developed to minimise the primary sources of carbon dioxide emissions. The anticipated environmental impact of the WST’s construction and operations will be thoroughly documented at the end of the study.