The Three Enclosures: palace, court and market in the sky
Ancient Chinese astronomers pictured the sky as a state: near the north pole stood the walled palace of the emperor of heaven, beside it the court where business was done, and further off a market. These three areas, fenced in by rows of stars like city walls, are the Three Enclosures. Together with the 28 mansions they form the frame of the Chinese sky.
Where each enclosure is
| Represents | Location | Western constellations | How to find it | |
|---|---|---|---|---|
| Purple Forbidden Enclosure (Zi Wei Yuan) | The emperor of heaven's palace | Around the north celestial pole | Ursa Minor, Draco, Cepheus, Camelopardalis | Find Polaris (Gou Chen Yi); two curving rows of stars, the left and right walls, enclose it |
| Supreme Palace Enclosure (Tai Wei Yuan) | The court, the government | South of the Dipper, north of the ecliptic | Leo, Virgo, Coma Berenices | On spring evenings, between Denebola at the tail of Leo and Virgo |
| Heavenly Market Enclosure (Tian Shi Yuan) | A market | West of the Milky Way, north of Scorpius | Hercules, Ophiuchus, Serpens | On summer evenings, southwest of the Summer Triangle: a large ring of faint stars |
Taipei, May 15, 10 p.m.. The maps show the sky as you look up: north at the top, east on the left; the center is the zenith and the rim is the horizon. Planets and the Moon are left out because they move from year to year; use the tool on this page to see a given night.
The Purple Enclosure: the pole star changes
Today's pole star is Polaris (α Ursae Minoris, Chinese Gou Chen Yi), just 0.6° from the north celestial pole and almost motionless. But precession swings the celestial pole around a great circle about every 26,000 years, so the job of pole star passes from star to star.
Running the precession formula backward: around 1000 BC, Polaris was still 17° from the pole, and the bright star closest to it was Kochab (β Ursae Minoris), about 7° away. In Chinese Kochab is called Di, "the Emperor", which is generally thought to be the reason. Polaris will keep closing in, to about 0.5° by the end of this century, and then slowly drift away.
Polaris stands at an altitude about equal to your latitude: roughly 25° in Taipei, 41° in New York, 51° in London. At Taipei's low latitude only the stars within 65° of the pole never set; further north, more of the Purple Enclosure stays up all night.
The Zi Wei star of astrology is not a star in the sky
Zi Wei Dou Shu (Purple Star Astrology) takes its name from the Purple Forbidden Enclosure, but the Zi Wei and Tian Fu stars on a chart are "virtual stars" calculated from your birth date and hour; none of them corresponds to a real star. The chart's Tan Lang, Ju Men, Lu Cun, Wen Qu, Lian Zhen, Wu Qu and Po Jun are Daoist names for the seven stars of the Big Dipper, and on a chart they too are calculated positions. See the Big Dipper and Zi Wei Dou Shu.
The Supreme Palace and the Heavenly Market
The Supreme Palace Enclosure lies between Leo and Virgo. Inside are asterisms like the Seats of the Five Emperors (Denebola, at Leo's tail, is the chief star), the Three Excellencies and the Nine Ministers: a court in the sky. The backward question mark of Leo's head is Xuanyuan in Chinese, and its brightest star, Regulus, is Xuanyuan Shisi.
The Heavenly Market Enclosure lies around Hercules and Ophiuchus. The stars in its walls are mostly named after ancient states such as Song, Han, Wei and Zhao, and inside are asterisms for measures, market stalls and butcher's shops. There are few bright stars here, so you need a dark site to see the whole ring.
Three common misconceptions
Polaris is the brightest star in the sky.
Polaris is only about magnitude 2; the brightest star is Sirius. Polaris matters because it barely moves, not because it is bright.
The pole star is always the same star.
Precession moves the celestial pole. Three thousand years ago the bright star nearest the pole was Kochab (the "Emperor" star); today it is Polaris; about 12,000 years from now it will be near Vega.
The Zi Wei star is Polaris.
The Zi Wei star of Zi Wei Dou Shu is a calculated virtual star. The Purple Enclosure in the sky is a region; Polaris lies within it, but the two are different things.
Tonight's sky: what is overhead right now
Pick a date, a time and a place to draw the whole sky at that moment, with the Moon, the planets, the bright stars that are up, and the Chinese lunar mansion crossing the meridian due south. Switch between Western constellation lines and Chinese asterisms. Everything is calculated in your browser.
Star catalog: about 1,600 Hipparcos stars brighter than magnitude 5 (compiled from d3-celestial, BSD license). The Moon and planets use simplified formulas accurate to within 0.3°; atmospheric refraction is ignored.
A straight word: this is astronomy, not fortune-telling
These pages are about stars you can actually see: where they are, which season brings them, and what East and West call them. The "mansion of the day" in the Chinese almanac, the twelve signs of Western astrology and the stars of Zi Wei Dou Shu all borrow star names, but they are separate systems of calculation and do not match what is in the sky that night. Everything on this site is for reference and entertainment.
Zi Wei Dou Shu: from star names to a birth chart
Zi Wei Dou Shu borrowed the names of the Purple Enclosure and the Big Dipper, but it is calculated in its own way. You can cast a free Zi Wei chart to see which palace each of the fourteen main stars lands in.
Three Enclosures FAQ
What are the Three Enclosures?
The Purple Forbidden Enclosure (around the north celestial pole, heaven's palace), the Supreme Palace Enclosure (around Leo and Virgo, the court) and the Heavenly Market Enclosure (around Hercules and Ophiuchus, the market).
Where is the Purple Forbidden Enclosure?
Around the north celestial pole, roughly covering Ursa Minor, Draco, Cepheus and Camelopardalis. Find Polaris; the region enclosed by two curving rows of stars around it is the Purple Enclosure.
Can you see the Zi Wei star of Zi Wei Dou Shu in the sky?
No. The stars of Zi Wei Dou Shu are virtual stars calculated from your birth time. Their names come from Chinese asterisms, but their positions have nothing to do with the real sky.