Charting the Chinese sky
WHILE the Greek astronomers Hipparchus and Ptolemy were cataloguing the stars as seen from the Mediterranean and dividing them into the patterns that we still know today, Chinese astronomers were developing a completely different celestial tradition in the far east. If China can be said to have an equivalent of Ptolemy and the star catalogue in the Almagest, it would be Chen Zhuo (c. AD 220–280) and the list of over 1,400 stars that he compiled. Chen himself post-dates Ptolemy by a century, but in his unnamed catalogue he collated observations by Chinese astronomers who worked several centuries before him, earlier even than the Greek Hipparchus.
As in the west, different sets of constellations were invented by different astronomers, although in China the final selection was fixed much earlier. Chen’s catalogue was a synthesis of the work of three previous authorities and their respective followers: Shi Shen and Gan De, who both lived around 300 BC; and Wuxian (or Wu Xian), whose dates are completely uncertain and who might even have been fictional. Shi Shen and his school is credited with 93 constellations, Gan De with 118, and Wuxian with 44, giving a total of 255.
Most of these constellations consisted of only a handful of stars, and some were just a single star; very few of the ancient Chinese constellations contained more than a dozen stars. There were no later additions to the Chinese constellation pantheon after Chen’s time, although some of the existing ones were modified.
Additional to these 255 star groups, and predating them, were 28 ancient divisions of the ecliptic known as xiu (formerly transliterated as hsiu), or mansions, as listed in the table below. These were vertical strips of sky that acted as markers for following the nightly progress of the Moon as it orbited the Earth each month, like a kind of zodiac, thereby providing the basis for a lunar calendar. Since the names of these mansions are so old, the origin and meaning of many of them is no longer understood.
THE 28 CHINESE LUNAR MANSIONS
Unlike the 12 houses of the zodiac familiar to western astrologers the 28 xiu were not equally spaced but varied considerably in width, from a mere 2° (Zi, the 20th mansion) to 33° (Jing, the 22nd), and stretched from pole to pole. Each xiu was named after a constellation within it, not necessarily on the ecliptic – another difference from western zodiacal constellations, all of which lie on the ecliptic.
Although Chen Zhuo’s original catalogue was lost some time in the 6th century, we know from later works that it contained 1,464 stars, over 400 more than the Almagest. When we talk of the Chinese sky and Chinese constellations, it is this blending of the three traditions of Shi Shen, Gan De, and Wuxian with the 28 xiu of the zodiac that we mean, giving a total of 283 constellations. What’s more, the Chinese system spread to Japan and Korea, so Chen’s catalogue and the maps made from it are the basis of a more general far-eastern tradition. This combined set of constellations remained in use until the early 17th century, when western constellations were introduced by Jesuit missionaries such as Adam Schall von Bell (1592–1666).
Chinese star charts
When Chinese celestial cartographers came to depict the sky, they at first used different colours to distinguish the constellations of the three different schools. Around AD 440 the Chinese astronomer Qian Lezhi made a bronze celestial globe (some describe it as a planisphere rather than a globe) on which the stars attributed to Shi Shen were shown in red, those of Gan De in black, and those of Wuxian in white (open circles). China was also the source of the first star charts on paper, the oldest known example being the Dunhuang chart, now thought to date from the mid to late 7th century AD.
Since Chinese constellations were symbolic, rather than pictorial as in the West, their member stars were usually not identified with any precision and could change over time. Hence there is considerable variance in the depiction and interpretation of Chinese constellations from different eras. These differences can be confusing and frustrating to anyone trying to reconstruct the Chinese sky.
Adding to the difficulty of identification is that Chinese astronomers made no attempt to convey the relative brightnesses of the stars by the sizes of the individual dots on their charts. This lack of interest in star magnitudes is characteristic of all Chinese (and Korean) star charts, and reveals an uncomfortable truth: they are primarily a canvas for the ruminations of astrologers, rather than a blueprint of the sky for scientific purposes. Chinese Emperors were considered to rule under a mandate from heaven, but this mandate could be revoked if they ruled badly; signs of heavenly displeasure would, it was thought, be seen in the form of celestial phenomena such as eclipses, comets, and ‘new’ stars (novae). So it was important for the Emperor and his advisors to know what such events meant whenever they occurred.
Given the various depictions and interpretations of constellations to be found in Oriental treatises down the ages, it seems that the size and shape of each constellation, as well as its significance, could be moulded at will to suit the requirements of the individual practitioner. By the time this Korean star chart, the Cheonsang yeolcha bunya jido, was drawn at the end of the 14th century, constellation shapes had become so stylized as to be almost meaningless astronomically.
FOUR COLOURFUL CHARACTERS
The Chinese divided the zodiacal region of the sky into four quarters, as shown at the right (click on it to see the original on the British Library’s website). Each quarter was associated with a cardinal point of the compass and with a season, and each was given the name of a mythical creature. Confusingly, there is more than one possible translation for several of the names, since they are very ancient and the original meanings are now uncertain. Each quarter contains 7 of the 28 xiu, or lunar mansions. The four sections of the sky are as follows:
1. The Blue (or Azure) Dragon of the east, cang long or qing long (its colour is sometimes described as green rather than blue); associated with spring. It consists of stars in the modern constellations Virgo, Libra, Scorpius, and Sagittarius. The dragon’s heart was represented by what the Chinese called the fire star, Huo, the modern Antares.
2. The Red (or Vermilion) Bird of the south, zhu que. It was associated with summer and consists of stars in the constellations Gemini, Cancer, Hydra, Crater, and Corvus.
3. The White Tiger of the west, bai hu, associated with autumn. It was formed from stars in the present-day Andromeda, Pisces, Aries, Taurus, and Orion.
4. The Black Tortoise (or Turtle) of the north, xuan wu, associated with winter. It is also known as the Black Warrior because the tortoise’s shell resembles a suit of armour. To add to the confusion, the tortoise is depicted with a large snake wrapped around it. The Black Tortoise was formed from stars in Sagittarius, Capricornus, Aquarius, and Pegasus.
These four divisions were later extended into a system of five celestial palaces, the additional fifth section being the circumpolar region known as the Purple Palace or Central Palace which incorporated Ursa Minor and parts of the modern constellations Camelopardalis, Draco, Cepheus, and Cassiopeia. This circumpolar region symbolized the central authority of the Emperor and hence was the most exalted of all.