The aim of this special session is to inform the astronomical community about the Wide-field Spectroscopic Telescope (WST) and involve colleagues in further shaping what will be a key facility in the 2040s.

The demand for a large telescope dedicated to spectroscopic surveys is an interest shared worldwide and figures explicitly in many national strategic science plans (e.g., European Astronet Roadmap 2023). Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work in synergy with future ground and space-based facilities.

WST is designed as a 12m aperture telescope with simultaneous operation of a large field-of-view (3 sq. degree), high-multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 arcmin integral field spectrograph (IFS). In only 5 years of operation, the MOS would target 250 million galaxies and 25 million stars at low spectral resolution plus 2 million stars at high resolution.

This special session dedicated to WST is extremely timely, since a dedicated 3-years concept study funded by the EU HORIZON programme (Project ID 101183153) started in February 2025. This is also the right time to prepare and propose WST as the next transformational ground-based astronomical facility answering the ESO call "Expanding Horizons".

The programme will include the presentation of the current status of the project, but the primary goal is to receive scientific input from the community. There will be time for a lively discussion of new ideas at the meeting, which will be followed up with the involvement of new people in the Science Team to further strengthen the involvement and leadership of the European astronomical community in this project.

Programme

• WST concept
• Cosmology science drivers
• Extra-galactic science drivers
• Galactic science drivers
• Time-domain science drivers
• Panel discussion

Invited speakers

• Roland Bacon (CRAL, FR)
• Jean-Paul Kneib (EPFL, CH)
• Jorryt Matthee (ISTA, AT)
• Vanessa Hill (OCA, FR)
• Richard Anderson (EPFL, CH)

Scientific organisers

• Vincenzo Mainieri (Chair, ESO Garching, DE)
• Sofia Randich (co-Chair, INAF, IT)
• Roland Bacon (CRAL, FR)
• Francesco Belfiore (INAF, IT)
• Richard Ellis (UCL, UK)
• Vanessa Hill (OCA, FR)
• Michele Moresco (University of Bologna, IT)
• Cyrielle Opitom (University of Edinburgh, UK)
• Paula Sanchez-Saez (ESO Garching, DE)
• Rodolfo Smiljanic (NCAC, PL)
• Eline Tolstoy (University of Groningen, NL)

Contact

vmainier @ eso.org