Deum Creatorem Venite Adoremus – Ninety Years of the Vatican Observatory at Castel Gandolfo
September 29, 2025, marks the 90th anniversary of the inauguration of the new headquarters of the Vatican Observatory at the Apostolic Palace of Castel Gandolfo. The Observatory is one of the oldest astronomical institutes in the world: its origins go back to the reform of the calendar from Julian to Gregorian in 1582. It was refounded in the Vatican by Pope Leo XIII in 1891 with the motu proprio Ut Mysticam.