(1Indiana University, Bloomington, Indiana | 2Ball State University, Muncie, Indiana, USA)

Keywords: archaeoastronomy, Stellarium, Ara Pacis, Monte Citorio Obelisk

This paper will show how it is possible and desirable to combine accurate cultural heritage 3D models of built features on the earth with a dynamic scientific model of the historical sky. Our case study concerns the northern Campus Martius in Rome where from 13-9 BC the Emperor Augustus commissioned the erection of two monuments: the Ara Pacis (“altar of peace”) and Monte Citorio Obelisk. The terrestrial model, based on new surveys of the monuments in question, was built using Maya. The celestial model was furnished by the open-source software, Stellarium, into which the terrestrial model was imported. We will show that there are several hundred million potential solutions to the problem of finding how, precisely, the Augustan designer aligned the sun, obelisk, and altar. In the traditional scholarship on the problem, no scholar has ever considered more than one date and moment in time. Both proposed solutions have been cogently criticized and may now be considered incorrect.
Stellarium supports a “big data” approach by generating any desired lighting solution in real time. Applying the rules of investigation implicitly developed by traditional scholarship, we show that the hundreds of millions of possible solutions can be convincingly narrowed down to two solar alignments determining the layout of the monuments on the ground in Rome. One alignment is seen from the east, the other from the west. Both alignments are closely related and culturally appropriate.