Archaeoastronomy in East Asia: Historical Observational Records ...

The dinosaurs, as well as nearly three quarters of all species in existence 65 million years ago, appear to have been wiped out by the impact in the Yucatan of an object with an estimated diameter up to 10 kilometers. North American megafauna may have met a similar fate at the end of the last Ice Age. The 1908 Tunguska event in Siberia, recently declassified United States Air Force data on objects entering Earth’s atmosphere, the discovery of increasing numbers of impact craters on the Earth, and the smashing into Jupiter of nearly two dozen fragments of Comet Shoemaker-Levy 9 in 1994 all demonstrate that collisions with NEOs pose a real and present danger. As a result, the study of historical records has assumed greater importance as a way of advancing research, for example, into the dynamic evolution of the orbits of short-period comets (Hasegawa, 1995).

Ho Peng-yoke (Ho, 1962; Ho & Ang, 1970) and Chen Zungui (Chen, 1984) made important contributions to the work of compiling historical records of cometary observations. The Comprehensive Catalog of Ancient Chinese Records of Astronomical Phenomena (Zhongguo gudai tianxiang jilu zong ji), compiled by the Beijing Observatory in 1988, expanded the scope of the historical sources surveyed to include local gazetteers from the entire country; however, this ambitious compilation is not without error.

To facilitate future research on the orbital evolution of NEOs, it was necessary to establish new selection criteria in order to collate all the potentially useful cometary records. The selection criteria established in compiling the present catalog of comet sightings are

1. First and foremost, the record must contain a description of the comet’s location that can serve to determine its path.

2. Records prior to the Han Dynasty (206 BC–AD 220), although vague, are included for their historical significance.

3. Records of “guest stars,” “anomalous stars,” and so forth are included on a case-by-case basis if the description mentions a tail or movement.

4. Reports in which observers mention sighting only the comet’s tail but no head, often using “vapor” (qi) to describe its appearance, are included on a case-by-case basis.