Thread by @Byzanzforscher

Our new paper: »The sun was darkened for 17 days« (AD 797). An Interdisciplinary Exploration of Celestial Phenomena between #Byzantium, #Charlemagne, and a #VolcanicEruption. #MedievalWorlds 17/2022: doi.org/10.1553/mediev… (1/9)
#Byzanzforschung, @imafo_oeaw

The blinding of the #Byzantine Emperor Constantine VI in #Constantinople in August 797 CE and his overthrow by his mother Eirene was used as legitimation for the #coronation of the Frankish King #Charlemagne as emperor of the Romans on 25 December, 800. (2/9)
@imafo_oeaw

In #Byzantine sources, Constantine VI´s #blinding was linked with a spectacular #celestialmanifestation of divine disapproval: “The #sun was darkened for seventeen days and did not emit its rays so that ships lost course and drifted about.” (3/9)
#Byzanzforschung

Research has so far mostly dismissed this description as an invention or as an exaggerated representation of a #solareclipse that took place shortly after or before the #blinding of the emperor. As we show, the considered eclipses were not visible in #Constantinople at all. (4/9)

Furthermore, the relevant sources clearly differentiate between a short-term #solareclipse and a longer term “veiling” of the #sun, as it happened also in the years #43BCE or #536CE after major volcanic eruptions. (5/9)
#Byzanzforschung

As we demonstrate, also the “#darkening” of #797CE can be connected to major #volcanic events and their atmospheric impacts. One candidate is a major #eruption dated to ca. 799/800 based on ice cores from #Greenland and tree rings from Northern and Central Europe. (6/9)

Another option are #eruptions on the Liparic Islands and of Mt. #Vesuvius mentioned in an eyewitness account of a cleric returning from #Constantinople to Rome after 787 CE. Ashes from Mt. Vesuvius had reached the #Bosporus already before in 472 CE. (7/9)

Furthermore, the late 8th century experienced several #coldanomalies after #volcanic eruptions as well as other celestial phenomena such as #auroras as far to the south as what is now south-eastern-Turkey due to massive solar storms connected with the "774/775CE-event". (8/9)

In total, atmospheric phenomena and climatic disturbances around #800CE allowed for a peculiar framing of the political events in the eyes of contemporary authors, who were confronted with the spectacular fall and rise of emperors at the #Bosporus and the #Tiber. (9/9)

We would like to thank the two anonymous reviewers for their most valuable comments and additions, as well as @THERA_4ever (Physics Institute, University of Bern) and Hisashi Hayakawa (Institute for Space-Earth Environmental Research, Nagoya University) for their advice.