Mao (Hairy Head)

Mao (Hairy Head) is the eighteenth 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 White Tiger of the West, the quadrant of the sky lying toward the west, 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, Mao is assigned the Cockerel.

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.

Mao, the Hairy Head, is the eighteenth of the twenty-eight xiu and the fourth mansion of the western palace, the White Tiger. It is identified with the Pleiades, the bright star cluster, one of the rare points where the Chinese, Indian, and Arabic lunar-mansion systems all name the same conspicuous group of stars, counted here as Mao, as the nakshatra Krittika, and as the manzil Al Thurayya. In the later astrological tradition its animal totem is the Rooster. As one of the twenty-eight lunar mansions Mao tracks 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; the Pleiades were among the most watched of asterisms across the ancient world.

That Mao, Krittika and Al Thurayya all independently fix on the Pleiades is one of the strongest single data points in the wider debate over how the three lunar-mansion systems relate historically, precisely because the cluster is compact and unmistakable enough that three unrelated traditions naming it separately, rather than one, is unsurprising, whereas the deeper agreement in total station count between the Chinese and Arabic systems, twenty-eight against the Indian twenty-seven, is harder to explain as mere coincidental convergence on an obvious object.