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Register a new userPresumable European aurorae in the mid AD 770s were halo displays
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Dagmar Neuhaeuser
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The interpretation of the strong 14-C variation around AD 775 as one (or several) solar super-flare(s) by, e.g., Usoskin et al. (2013) is based on alleged aurora sightings in the mid AD 770s in Europe: A red cross/crucifix in AD 773/4/6 from the Anglo-Saxon Chronicle, inflamed shields in AD 776 (both listed in the aurora catalogue of Link 1962), and riders on white horses in AD 773 (newly proposed as aurora in Usoskin et al. 2013), the two latter from the Royal Frankish Annals. We discuss the reports about these three sightings in detail here. We can show that all three were halo displays: The red cross or crucifix is formed by the horizontal arc and a vertical pillar of light (either with the Sun during sunset or with the moon after sunset); the inflamed shields and the riders on white horses were both two mock suns, especially the latter narrated in form of a Christian adaptation of the antique dioscuri motive. While the latter event took place early in AD 774 (dated AD 773 in Usoskin et al. 2013), the two other sightings have to be dated AD 776, i.e. anyway too late for being in connection with a 14-C rise that started before AD 775. We also sketch the ideological background of those sightings and there were many similar reports throughout that time. In addition, we present a small drawing of a lunar halo display with horizontal arc and vertical pillar forming a cross for shortly later, namely AD 806 June 4, the night of full moon, also from the Anglo-Saxon Chronicle; we also show historic drawings of solar and lunar halo crosses from G. Kirch and Helevius and a modern photograph.
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Given that a strong 14C variation in AD 775 has recently been suggested to be due to the largest solar flare ever recorded in history, it is relevant to investigate whether celestial events observed around that time may have been aurorae, possibly even very strong aurorae, or otherwise related to the 14C variation (e.g. a suggested comet impact with Earths atmosphere). We critically review several celestial observations from AD 757 to the end of the 770s, most of which were previously considered to be true, and in some cases, strong aurorae; we discuss in detail the East Asian records and their wording. We conclude that probably none among the events after AD 770 was actually an aurora, including the event in AD 776 Jan, which was misdated for AD 774 or 775; the observed white qi phenomenon that happened above the moon in the south-east was most probably a halo effect near the full moon - too late in any case to be related to the 14C variation in AD 774/5. There is another report of a similar (or identical) white qi phenomenon above the moon, reported just before a comet observation and dated to AD 776 Jan; the reported comet observed by the Chinese was misdated to AD 776, but actually sighted in AD 767. Our critical review of East Asian reports of aurorae circa AD 775 shows some very likely true Chinese auroral displays observed and reported for AD 762; there were also several events prior to AD 771 that may have been aurorae but are questionable.
The recently published Yemeni observing report about SN 1006 from al-Yamani clearly gives AD 1006 Apr $17 pm 2$ (mid-Rajab 396h) as first observation date. Since this is about 1.5 weeks earlier than the otherwise earliest reports (Apr 28 or 30) as discussed so far, we were motivated to investigate an early sighting in more depth. We searched for additional evidences from other areas like East Asia and Europe. We found that the date given by al-Yamani is fully consistent with other evidence, including: (a) SN 1006 rose several times half an hour after sunset (al-Yamani), which is correct for the location of Sana in Yemen for the time around Apr 17, but it would not be correct for late Apr or early May; (b) the date (3rd year, 3rd lunar month, 28th day wuzi, Ichidai Yoki) for an observation of a guest star in Japan is inconsistent (there is no day wuzi in that lunar month), but may be dated to Apr 16 by reading wuwu date rather than a wuzi date; (c) there is observational evidence that SN 1006 was observed in East Asia early or mid April; for the second half of April, a bad weather (early monsoon) period is not unlikely -- there is a lack of night reports; (d) the observer in St. Gallen reported to have seen SN 1006 for three months, which must have ended at the very latest on AD 1006 Jul 10, given his northern location, so that his observations probably started in April. We conclude that the correctly reported details give quite high confidence in the fully self-consistent report of al-Yamani, so that the early discovery date should be considered seriously.
In a previous work, we establish that the acclaimed Arabic records of SN 1054 from ibn Butlan originate from Europe. Also, we reconstructed the European sky at the time of the event and find that the new star (SN 1054) was in the west while the planet Venus was on the opposite side of the sky (in the east) with the Sun sited directly between these two equally bright objects, as documented in East-Asian records. Here, we investigate the engravings on tombstones (stecci) from several necropolises in present-day Bosnia and Herzegovina (far from the influence of the Church) as a possible European record of SN 1054. Certainly, knowledge and understanding of celestial events (such as supernovae) were somewhat poor in the mid-XI century.
Although governments across Europe had realised the need to incentivise the development of practically viable longitude solutions as early as the late-sixteenth century, the English government was late to the party. An sense of urgency among the scientific community and maritime navigators led to the establishment of a number of longitude awards by private donors. The first private British award was bequeathed in 1691 by Thomas Axe, parish clerk of Ottery St. Mary (Devon). Despite the absence of an expenses component and the onerous and costly nature of its terms and conditions, the Axe prize attracted a number of optimistic claimants. Although the award was never disbursed, it may have contributed to the instigation of the government-supported monetary reward associated with the British Longitude Act of 1714. It is likely that the conditions governing the British Longitude Prize, specifically the required accuracy and the need for sea trials and of disclosure of a successful methods theoretical principles, can be traced back at least in part to the Axe Prize requirements.
Despite frequent references in modern reviews to a seventeenth-century Venetian longitude prize, only a single, circumstantial reference to the alleged prize is known from contemporary sources. Edward Harrisons scathing assessment of the conditions governing the award of an alleged Venetian longitude prize simultaneously disparages the rewards offered by the Dutch States General. However, the latter had long run its course by 1696, the year of the citation, thus rendering Harrisons reference unreliable. Whereas other longitude awards offered by the leading European maritime nations attracted applicants from far and wide, often accompanied by extensive, self-published pamphlets, the alleged Venetian prize does not seem to have been subject to similar hype. The alleged existence of seventeenth-century Venetian award is particularly curious, because the citys fortune was clearly in decline, and longitude determination on the open seas does not appear to have been a priority; the citys mariners already had access to excellent portolan charts. It is therefore recommended that authors refrain from referring to a potentially phantom Venetian longitude prize in the same context as the major sixteenth- to eighteenth-century European awards offered by the dominant sea-faring nations.
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