Dating the foundation of Augusta Taurinorum ex sole. The augustean propaganda and the role of Astronomy

Abstract

The essay presents the results of a joint study of astronomy and archeology that has allowed to define the foundation date of the city of Turin as a Roman colony, called Iulia Augusta Taurinorum. This multidisciplinary research represents a new reading of the historical-archaeological sources and the use of astronomy according to the Etruscan-Latin gromatica. By taking into consideration the apparent motion of a True Sun, the possible measurement errors, the atmospheric refraction and the elevation of the horizon, and the Julian date in use in astronomy, a numerical program has been elaborated to define the coincidences of the calendars between the azimuth of the main road axis and the course of the sun. For a series of very particular historical and contextual conditions it was therefore possible to trace with sufficient accuracy the day and the year of foundation of the city: January 30, 9 BC, which coincides, not surprisingly, with a particularly important anniversary for Ottaviano Augusto, Emperor from 27 BC to 14 AC. In fact, the astronomical data interfaced with the archaeological, epigraphic and written sources suggest that Turin was born at the end of the Alpine wars, concluded after the acquisition of the Valle di Susa and, more extensively, of the Maritime Alps, Pennine and Graie. Founded as a colony along the road leading to the Gauls, Augusta Taurinorum was inaugurated on the day of the anniversary of the feast of Pax, established by Augustus and celebrated at the Ara Pacis in Rome starting from 9 BC. The large marble altar of Campo Marzio was, as matter of fact, built to celebrate the end of civil wars and the beginning of a new era (confirmed also by the astrological/astronomical ephemerides of that time), which is widely reported in the official Augustean literature.