4:15 PM - 4:30 PM
[MIS22-08] Planetary observations in the Aska period inferred from the Kitora star map
Keywords:Kitora tumulus, Star map, Yourou code, Ecliptic, Twenty-eight mansions
The Kitora tumulus in Aska village, Nara prefecture, has been intensively investigated since 1983. It is estimated to have been erected in the late 7th or early 8th century in the south of the capital at the time. It has mural paintings in the chamber. They are four divine creatures on the wall and a star map on the ceiling. The star map consists of more than 219 stars represented by gold foil circles, red lines connecting stars to represent more than 64 constellations, and four red circles. Three red circles are concentric, and inferred as the internal and outer circles, and the equator. The center of the other circle is shifted north-west of the center of the other three circles. This shifted circle has been inferred to represent the ecliptic although its relative location to stars is largely shifted from the actual location. This mis-location of the ecliptic has been interpreted to be caused by the painter's mistake or intentional modification for decorative purpose. These interpretations imply that astronomical knowledge was not valued and/or very limited at the time in the capital. In this presentation, it is shown that this mis-location would be conducted intentionally to avoid the restriction of the law. The Yoro code, the penal and administrative laws enfoced after 757, prohibited the personal possession and to bring out the equipment for the astronomical observation. Although the Kitora tumulus is estimated to be erected before the Yoro code, it can be speculated that similar code was implemented at the time. Considering this intentional mis-location of the ecliptics, the Kitora star map provides us the information of the astronomical observation, especially the observation of planets in the Aska period, the pioneering period of planetary observations in Japan.