The Chinese comet observation in AD 773 January

Abstract

The strong 14C increase in the year AD 774/5 detected in one German and two Japanese trees was recently suggested to have been caused by an impact of a comet onto Earth and a deposition of large amounts of 14C into the atmosphere (Liu et al. 2014). The authors supported their claim using a report of a historic Chinese observation of a comet ostensibly colliding with Earth's atmosphere in AD 773 January. We show here that the Chinese text presented by those authors is not an original historic text, but that it is comprised of several different sources. Moreover, the translation presented in Liu et al. is misleading and inaccurate. We give the exact Chinese wordings and our English translations. According to the original sources, the Chinese observed a comet in mid January 773, but they report neither a collision nor a large coma, just a long tail. Also, there is no report in any of the source texts about "dust rain in the daytime" as claimed by Liu et al. (2014), but simply a normal dust storm. Ho (1962) reports sightings of this comet in China on AD 773 Jan 15 and/or 17 and in Japan on AD 773 Jan 20 (Ho 1962). At the relevant historic time, the Chinese held that comets were produced within the Earth's atmosphere, so that it would have been impossible for them to report a "collision" of a comet with Earth's atmosphere. The translation and conclusions made by Liu et al. (2014) are not supported by the historical record. Therefore, postulating a sudden increase in 14C in corals off the Chinese coast precisely in mid January 773 (Liu et al. 2014) is not justified given just the 230Th dating for AD 783 \pm 14.Comment: 4 pages with one figure, paper in press in Astronomical Notes 201

A review of East Asian reports of aurorae and comets circa AD 775

“…However, as we have shown already (Chapman et al 2014), this claim was not correct for several reasons:…”

“…The two Chinese comet reports in the mid AD 770s also do not relate to the 14 C increase: The comet of January 773 did not collide with the Earth's atmosphere (Chapman et al 2014), and the comet reported for AD 776 was actually observed nine years earlier (Sect. 5.2).…”

“…2. The Chinese report presented in Liu et al (2014) See Chapman et al (2014) for details. This case was reexamined by Stephenson (2015) and fully confirmed.…”

“…Both Usoskin & Kovaltsov (2014) and Melott (2014) showed that comets could not have delivered as much 14 C as needed for the AD 775 variation. Then, Chapman et al (2014) clarified that the Chinese comet observed AD 773 January 17 was a normal comet with a long tail, which was then also observed in Japan three days later, and thus could not have collided with the Earth on January 17. Usoskin et al (2013) claimed to have found a distinct cluster of aurorae between AD 770 and 776 which suggests a high solar activity level around AD 775.…”

A solar super‐flare as cause for the 14C variation in AD 774/5?

“…www.an-journal.org Chapman et al (2014) show that the original Chinese texts about this comet just report about a very normal comet observed in China on or since AD 773 Jan 17 (also observed in Japan on or since Jan 20), and that the material presented in Liu et al (2014) is misleading: There is no evidence for a collision of a comet with Earth.…”