Solar Physics

, 294:42 | Cite as

The Celestial Sign in the Anglo-Saxon Chronicle in the 770s: Insights on Contemporary Solar Activity

  • Hisashi HayakawaEmail author
  • F. Richard Stephenson
  • Yuta Uchikawa
  • Yusuke Ebihara
  • Christopher J. Scott
  • Matthew N. Wild
  • Julia Wilkinson
  • David M. Willis


The anomalous concentration of radiocarbon in 774/775 attracted intense discussion on its origin, including the possible extreme solar event(s) exceeding any events in observational history. Anticipating such extreme solar events, auroral records were also surveyed in historical documents and those including the red celestial sign after sunset in the Anglo-Saxon Chronicle (ASC) were subjected to consideration. Usoskin et al. (Astron. Astrophys. 55, L3, 2013: U13) interpreted this record as an aurora and suggested enhanced solar activity around 774/775. Conversely, Neuhäuser and Neuhäuser (Astron. Nachr. 336, 225, 2015a: N15a; Astron. Nachr. 336, 913, 2015b: N15b) interpreted “after sunset” as during sunset or twilight; they considered this sign as a halo display and suggested a solar minimum around 774. However, so far these records have not been discussed in comparison with eyewitness auroral records during the known extreme space weather events, although they were discussed in relationship with potential extreme events in 774/775. Therefore, we reconstruct the observational details based on the original records in the ASC and philological references, compare them with eyewitness auroral observations during known extreme space weather events, and consider contemporary solar activity. We clarify the observation was indeed “after sunset”, reject the solar-halo hypothesis, define the observational time span between 25 March 775 and 25 December 777, and note that the parallel “drawing of lunar halo display” in 806 in the ASC shown in N15b was not based on the original observation in England. We show examples of eyewitness auroral observations during twilight in known space weather events, and this celestial sign does not contradict the observational evidence. Accordingly, we consider this event to have happened after the onset of the event in 774/775, but to have shown relatively enhanced solar activity, with regard to other historical auroral records in the mid-770s, as also confirmed by the 10Be data from ice cores.


Solar–terrestrial relationships Aurora CME History of astronomy 



We thank Corpus Christi College (the University of Cambridge), the British Library, the Fitzwilliam Museum (the University of Cambridge), and Staatsbibliothek zu Berlin (SBB) for providing the images and the permissions of research of the manuscripts of Anglo-Saxon Chronicle, those of Anglo-Saxon coins, and those of Annales Laudensis et Sancti Vincentii. We gratefully acknowledge L. Cowley for providing HaloSim 3, R. Naismith for his advice on the contemporary coinage, A. Popescu for permission of photographing Anglo-Saxon coins in the Fitzwilliam Museum (the University of Cambridge), D. Hooper for advices on atmospheric optics, the archivist in SBB for his permission of reproduction and advices on precise referencing of the MS Phillipps 1830, Y. Okada for his help on accessing German documents, S. Kikuchi for his advices on the Carolingian military systems, the Carolingian manuscripts, and medieval Latin dictionaries for the Carolingian territories, N. Ebihara for her comments on our philological interpretation on the Old English texts, K. Nakada for his advice on the medieval European military systems, and T. Hoshi for providing calculation code for sunset and sunrise. This work was supported by the UKSSDC, a NSF grant ANT-1643700, and a Grant-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology of Japan, Grant Number JP18H01254 (PI: H. Isobe), JP15H05816 (PI: S. Yoden), JP15H03732 (PI: Y. Ebihara), JP16H03955 (PI: K. Shibata), and JP15H05815 (PI: Y. Miyoshi), and a Grant-in-Aid for JSPS Research Fellows JP17J06954 (PI: H. Hayakawa).

Disclosure of Potential Conflict of Interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Science and Technology Facilities CouncilRutherford Appleton LaboratoryDidcotUK
  2. 2.Graduate School of LettersOsaka UniversityToyonakaJapan
  3. 3.Department of PhysicsUniversity of DurhamDurhamUK
  4. 4.Graduate School of Humanities and SociologyThe University of TokyoTokyoJapan
  5. 5.The Fitzwilliam MuseumUniversity of CambridgeCambridgeUK
  6. 6.Research Institute for Sustainable HumanosphereKyoto UniversityGokasho, UjiJapan
  7. 7.Unit of Synergetic Studies for SpaceKyoto UniversityKyotoJapan
  8. 8.Department of MeteorologyUniversity of ReadingReadingUK
  9. 9.Zooniverse, c/o Astrophysics DepartmentUniversity of OxfordOxfordUK
  10. 10.Centre for Fusion, Space and Astrophysics, Department of PhysicsUniversity of WarwickCoventryUK

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