Last November 4th a contract was signed to fund the conceptual study of a new telescope, the Wide Field Spectroscopic Telescope (WST), which could become operational in Chile after 2040. The consortium leading the WST project will receive three million euros to fund a detailed conceptual study over the next three years, from 2025 to 2027. The innovative WST project aims to build a telescope dedicated entirely to wide-field spectroscopic surveys in the optical band, covering all types of celestial objects—from distant galaxies to asteroids and comets within our Solar System. The project was selected as part of the European Union’s Horizon Europe Framework Program through a competitive call for research infrastructures.
WST facility design. Credit: G.Gausachs/WST
The international consortium that received the funding aims to propose WST as the next major observatory infrastructure of the European Southern Observatory (ESO), following the completion of the Extremely Large Telescope (ELT), currently under construction in the Chilean Andes. This consortium includes 19 research institutions across Europe and Australia, with a science team of over six hundred members from 32 countries distributed in all five continents.
ICRAR-UWA is co-lead of the WST survey design package that will define what the facility will observe during its first few years.
“The wide-field spectroscopic telescope will allow us to map the dark matter distribution across the Universe, and with the SKA in WA how matter has transformed from gas to stars and dust since the Big Bang,” said Professor Simon Driver, from ICRAR’s UWA node.
WST will address many open questions in astrophysics over an extensive range of physical scales: from the formation of the large-scale structures in the early universe, to the interplay of galaxies in the cosmic web, to the formation of our own Galaxy, to the evolution of stars and the formation of planets around them. Credit: WST/V.Springel,Max-Planck-Institut für Astrophysik/ESO
The project is led by Roland Bacon of Centre National de la Recherche Scientifique (CNRS, France) and Sofia Randich of National Institute for Astrophysics (INAF, Italy), with the support of the project office and a Steering Committee with members from the involved institutes. WST promises to fulfil a critical need identified by the international scientific community: a telescope with a 10-metre class primary mirror exclusively dedicated to the spectroscopic observations of celestial sources. The demand for such an observational infrastructure is explicitly stated in numerous strategic international scientific plans outlining the critical priorities for astrophysical research in the coming decade, including the European Astronet Roadmap 2023.
Despite ongoing construction of ground-based telescopes with 30-40 meter mirrors, there are no existing or planned facilities with WST unique characteristics: namely, a 12-metre primary mirror diameter, simultaneous operations of a multi-object spectrograph (MOS) capable of observing over a large field of view (three square degrees, approximately the area of 12 full Moons) with high “multiplex” capabilities (20,000 fibres), along panoramic integral field spectrograph (IFS), which covers an apparent surface area of sky of 9 square arc minutes.
“These specifications are highly ambitious and position the WST project above existing and planned ground-based observational infrastructures. In just five years, the MOS would acquire spectra from 250 million galaxies and 25 million stars at low spectral resolution, plus over 2 million stars at high resolution, while the IFS would provide 4 billion spectra, enabling researchers to fully characterise these sources. To put these figures into perspective, it would take 43 years to obtain the same 4 billion spectra using the IFS available on ESO’s VLT telescope or 375 years using the upcoming 4MOST instrument to observe 250 million galaxies at the same depth,” says Roland Bacon.
Sofia Randich explains: “The Wide Field Spectroscopic Telescope will produce cutting-edge, transformative science and will allow researchers to tackle key scientific questions in areas such as cosmology; the formation, evolution, and chemical enrichment of galaxies (including the Milky Way); the origin of stars and planets; astrophysics of transient or time-variable events; and multi-messenger astrophysics.”
The concept study funded by Horizon Europe will address all relevant aspects needed to form a comprehensive picture: the telescope design and instruments, the selection of the site in Chile where the telescope will be located, further development of scientific cases, the preparation of a survey plan, as well as an operational model for the facility and plans for innovative data reduction and analysis, to maximize scientific return.
The study will pay particular attention to environmental sustainability. Environmental impact will be one of the criteria guiding technological choices and trade-offs, and solutions will be developed to mitigate significant sources of carbon dioxide emissions. The projected environmental impact for the construction and operational phases of the WST will be documented in detail at the end of the study.
Shortly, ESO will open a call for ideas to evaluate the most innovative and science-promising projects for investment after ELT is completed, with its first light expected in 2028. If approved, WST would become the next major ESO facility, with the potential to address groundbreaking astrophysical questions in the 2040s.
Visit the WST website: https://www.wstelescope.com/
