Revisiting the epoch of the earliest Chinese star catalog titled “Shi Shi Xing Jing”

Abstract

Abstract The Shi Shi Xing Jing (SSXJ) is known to be the earliest star catalog in Chinese history. Its epoch of observation has long been a matter of debate. In recent studies, Sun Xiaochun pointed out that the observations must have been made using meridian instruments and developed a so-called Fourier method to determine the epoch, while Tsuko Nakamura developed a χ2 method to determine the epoch and showed that the measurement error can be estimated using bootstrap resamplings. However, they did not take both meridian measurements and bootstrap resamplings into consideration simultaneously. Hence, in this paper we determine the epoch and its uncertainty by applying the two methods and performing the bootstrap resamplings in a careful manner. We adopt identifications of the reference stars of 116 asterisms with stars in modern catalogs, including the determinative stars or the reference stars for the 28 lunar lodges. We find that the stars can be divided into four groups. Twenty-five of the 28 determinative stars are estimated to have been observed around 65 ± 28 BCE, corresponding to either Xianyu Wangren’s observation in 78–76 BCE or Geng Shouchang’s observation in 52 BCE. The other stars make three groups: the main group composed of 63 reference stars has an observation epoch of 108 ± 16 BCE corresponding to Luoxia Hong’s observation in 104 BCE; another group of eight reference stars including two determinative stars has an observation epoch of 200 ± 45 BCE, corresponding to the establishment of the Former Han dynasty; and the other group of 13 reference stars including one determinative star has an observation epoch of approximately 100 ± 35 CE, corresponding to the observations by ecliptic instruments in 103 CE following Gia Kui’s suggestion of 92 CE. In conclusion, the SSXJ has a few temporal strata of observations made through the Han dynasty.