Origin 433 BCE
The eleventh mansion lies across Aquarius and Equuleus. Associated with death, mourning and the tomb, it is a solemn and often inauspicious lodge in the selection almanacs. Its name refers to the emptiness of that region of sky, which holds no bright stars, and the naming shows the lodges were fixed by what could actually be seen rather than by a scheme requiring each division to be equally furnished. Faint regions produced faint reference stars and, in several cases, uncomfortably wide lodges. Sky of this kind is nonetheless useful for calendar work, since a faint field makes the moon's position against it easier to judge.
Facts
Identity
Equatorial Extent (Du)10 du (about 9.9 degrees of equatorial arc) 2Tradition: Han-era Shi Shen tradition (Kaiyuan Zhanjing) Du: the arc-degree unit of the classical Chinese calendar, where a full circle equalled 365 and a quarter du (about 0.9856 modern degrees per du). This width is the Han-era figure standardized under the Taichu calendar and preserved in the Tang-dynasty Kaiyuan Zhanjing's Shi Shen star table; later dynasties recorded small revisions as precession shifted the determinative stars, so this is one epoch's figure, not a timeless constant. It measures the mansion's extent along the celestial equator (right ascension), the coordinate system Chinese astronomy actually used, not a position on the ecliptic (tropical zodiac); the atlas has no sourced mapping from this equatorial system onto a start point in ecliptic longitude, so this figure alone cannot be substituted into a start-end boundary range the way the equal Arabic-mansion spans are. Determinative StarBeta Aquarii 2Tradition: Han-era Shi Shen tradition (Kaiyuan Zhanjing) Origins
Origin Period433 BCE 1Tradition: Chinese equatorial astronomy Origin PeriodThe full set of twenty-eight lunar mansions is attested together for the first time on the lacquer box from the tomb of Marquis Yi of Zeng, sealed in 433 BCE, the earliest surviving object to record the complete list of names. 1 Origin of the NameThe English "lunar mansion" is borrowed from the Indian nakshatras and the Arabic manazil and misdescribes the xiu. A xiu is a lodge marked by a determinative star and measured in right ascension along the celestial EQUATOR; it is not a division of the Moon's ecliptic path, and the three systems are not variants of one scheme. 2 Attributions
PalaceBlack Tortoise of the North 1 Learn More
The Lunar Mansion Xu (Emptiness)
Xu (Emptiness) is the eleventh of the twenty-eight xiu, the lunar mansions of traditional Chinese astronomy. Each xiu is a segment of the sky marked by a group of stars near the celestial equator, and together they divide the heavens into the belt through which the sun, moon and planets appear to move.
Palace, animal and place in the sky
This mansion belongs to the Black Tortoise of the North, the quadrant of the sky lying toward the north, one of the four symbolic creatures among which the twenty-eight are shared out seven to each. In the later scheme that pairs every mansion with a creature, Xu is assigned the Rat.
The twenty-eight mansions are among the oldest elements of Chinese sky-lore, attested well before the common era and used to track the nightly progress of the moon and to fix the calendar. The system is described here as that documented astronomical and calendrical tradition, from which its astrological uses later grew.
Xu, the Emptiness of the Black Tortoise
Xu, the Emptiness, is the eleventh of the twenty-eight xiu and the fourth mansion of the northern palace, the Black Tortoise, the central mansion of the winter quarter. Its name means void or emptiness, identified with stars in Aquarius and Equuleus, and it was anciently associated with the winter solstice and with death, ruins, and mourning. In the later astrological tradition its animal totem is the Rat. As one of the twenty-eight lunar mansions it marks a portion of the Moon's path. These are the conventions of the Chinese astronomical and calendrical tradition, in which the twenty-eight xiu divide the sky into four palaces of seven mansions, the Black Tortoise spanning the northern heavens the almanac ties to winter and the deep cold.
Xu's old association with the winter solstice, death and mourning places it at a structural low point comparable to how the Arabic Al Baldah and the Vedic Uttara Ashadha region mark their own respective quiet or empty stretches of the ecliptic, though the three traditions arrive at broadly similar "quiet point" readings by entirely different routes, in this case the calendrical logic of the solstice as the year's dead centre rather than the sparseness of visible stars, which the Arabic mansion's empty patch depends on instead.
Cross-Tradition Connections
Associated With
Named as the emblem animal of the lunar mansion Xu (Emptiness) in the twenty-eight xiu list.
Contained In
One of the seven lunar lodges of this palace.
Originates in Language
Sources
1. Astrology and Cosmology in Early China: Conforming Earth to Heaven
David W. Pankenier, Cambridge University Press, 2013On the twenty-eight lodges and the Zeng Hou Yi lacquer chest
2. Science and Civilisation in China, Volume 3: Mathematics and the Sciences of the Heavens and the Earth
Joseph Needham, Cambridge University Press, 1959Vol. 3, the section on astronomy: the hsiu (lunar mansions), the equatorial system and the du measureQuote, Vol. 3, the section on astronomy: the hsiu (lunar mansions), the equatorial system and the du measure
The twenty-eight lodges are equatorial divisions bounded by determinative stars and so of unequal width, measured in du on a circle of 365.25 parts; their relation to the Indian and Arabic lunar mansion systems is unresolved.
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