Autor Thema: AD 775 - Komet, Nova oder Bolide?  (Gelesen 992 mal)

Offline karmaka

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AD 775 - Komet, Nova oder Bolide?
« am: August 14, 2014, 13:54:18 nachm. »
AD 775 - Komet, Nova oder Bolide?

The Chinese comet observation in AD 773 January

Jesse Chapman, Mark Csikszentmihalyi (U Berkeley), Ralph Neuhaeuser (U Jena)

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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.


A transient event in AD 775 reported by al-Tabari: A bolide - not a nova, supernova, or kilonova

Ralph Neuhaeuser (U Jena), Paul Kunitzsch (LMU Munich)

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Given that the cause for the strong increase in 14C in AD 774/5 in Japanese and German trees is still a matter of debate (e.g. short Gamma-Ray Burst or solar super-flare), we have searched in Arabic chronicles for reports about unusual transient celestial events. In the {\em History of al-Tabari we found two (almost identical) reports about such an event. The group around caliph al-Mansur observed a transient event while on the way from Baghdad to Mecca on AD 775 Aug 29 - Sep 1 (Julian calendar), most probably during the morning twilight of AD 775 Aug 29. A celestial object kawkab was seen to fall or set inqadda, and its trace atharuhu was seen for at least tens of minutes (up to 70-90 min) during morning twilight. The reports use the Arabic words kawkab and athar(uhu), which were also used in the known Arabic reports about supernovae SN 1006 and 1054, so that one might consider an interpretation as a nova-like event. The kawkab (celestial object) was observed only during the morning twilight at a brightness of probably between about -3 and 0 mag. Such a brightness and time-scale would be expected for optical kilonovae (at 3 to 9 kpc) in the context of short Gamma-Ray Bursts. There are no similar reports from eastern Asia for this time. However, the short reports are fully consistent with a bolide: The word kawkab can be used for meteor, the verb inqadda normally means "falling down", the word atharuhu can mean "its trace". We therefore prefer the interpretation as bolide. We discuss in detail how to convert the Muslim calendar date to a date in the Julian calendar using first the calculated Islamic calendar and then considering the time when the crescent new moon could be visible at the given location.

Bezug:

Mysterious abrupt carbon-14 increase in coral contributed by a comet

Yi Liu et al

Scientific Reports 4, Article number: 3728
doi:10.1038/srep03728
Published 16 January 2014

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Offline karmaka

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Re: AD 775 - Komet, Nova oder Bolide?
« Antwort #1 am: Januar 02, 2015, 11:01:29 vorm. »
Rapid increase in cosmogenic 14C in AD 775 measured in New Zealand kauri trees indicates short-lived increase in 14C production spanning both hemispheres

D. Güttler, F. Adolphi, J. Beer, N. Bleicher, G. Boswijk, M. Christl, A. Hogg, J. Palmer, C. Vockenhuber, L. Wacker, J. Wunder

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Here we present the first annually resolved Southern Hemisphere (SH) 14C record spanning the interval AD 760–787, using New Zealand kauri (Agathis australis  ) chronology wood. An almost identical distinct increase compared to Northern Hemisphere data was observed, suggesting a cosmic event with globally uniform impact as a potential cause for the increase.

 

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