50th Anniversary Meeting
A landmark gathering celebrating half a century of GEOS activity.
In 2025, GEOS members convened in Nantes to celebrate the 50th anniversary of the European Group on Stellar Observations. Founded in 1975—although active even earlier—GEOS marked this milestone with an in‑person meeting, making the Nantes reunion particularly meaningful for the community.
The city of Nantes provided a fitting backdrop for the anniversary, with its historic centre, university heritage, and rich cultural environment. The meeting was organized by Guy Boistel and Jean‑François Le Borgne, who prepared a well‑balanced scientific program combining historical insight, current research, and future directions.
Participants revisited the origins of the Group, including early debates around the validity of visual estimates and GEOS’s pioneering adoption of rigorous statistical approaches to strengthen observational reliability. RR Lyrae stars—central to GEOS activity since its foundation—were a major focus, along with renewed interest in the long‑term visual monitoring of Cepheids.
Scientific presentations covered a broad range of topics: Ennio Poretti discussed an ongoing study of the binary‑system candidate KIC 2831097; Mercé Correa presented the Europlanet telescope network; Marc Serrau introduced a tool for extracting variable‑star data from the Gaia EDR3 catalog; and additional speakers shared results on objects such as CoRoT‑10 and highlighted the growing role of modern “smart telescopes.” Round‑table discussions expanded on observational strategies and the future organization of the Group.
The anniversary celebration concluded with a gala dinner at the historic LU biscuit factory, now a restaurant, where participants toasted fifty years of GEOS activity.
