The Zodiac Constellations: Where the Sun Really Is
"I'm a Scorpio" means that when you were born the Sun was in the astrological sign of Scorpio. But if you could look at the stars behind the Sun that day, it probably wasn't in the constellation Scorpius at all. Nobody made a mistake: the constellations in the sky and the signs of astrology are simply two different things.
Where the Sun actually is in 2027
| Constellation (IAU boundaries) | Sun inside | Days | Astrology sign of the same name |
|---|---|---|---|
| Capricornus | Jan 20 – Feb 16 | 28 | Capricorn Dec 22 – Jan 19 |
| Aquarius | Feb 17 – Mar 12 | 24 | Aquarius Jan 20 – Feb 17 |
| Pisces | Mar 13 – Apr 18 | 37 | Pisces Feb 18 – Mar 19 |
| Aries | Apr 19 – May 14 | 26 | Aries Mar 20 – Apr 19 |
| Taurus | May 15 – Jun 21 | 38 | Taurus Apr 20 – May 20 |
| Gemini | Jun 22 – Jul 20 | 29 | Gemini May 21 – Jun 20 |
| Cancer | Jul 21 – Aug 10 | 21 | Cancer Jun 21 – Jul 22 |
| Leo | Aug 11 – Sep 16 | 37 | Leo Jul 23 – Aug 22 |
| Virgo | Sep 17 – Oct 31 | 45 | Virgo Aug 23 – Sep 22 |
| Libra | Nov 1 – Nov 23 | 23 | Libra Sep 23 – Oct 22 |
| Scorpius | Nov 24 – Nov 29 | 6 | Scorpio Oct 23 – Nov 21 |
| Ophiuchus | Nov 30 – Dec 18 | 19 | (astrology has no Ophiuchus) |
| Sagittarius | Dec 19 – Jan 20 | 33 | Sagittarius Nov 22 – Dec 21 |
Sun positions computed day by day with astronomy-engine and assigned to constellations by the IAU boundaries published in 1930 (dates are UTC dates, the same time zone as our zodiac sign pages; elsewhere a boundary day can differ by one). Astrology dates are the moments the Sun's ecliptic longitude crosses each multiple of 30°, for 2027.
Put side by side, the difference is plain. Constellations come in all sizes: the Sun spends 45 days in Virgo but only 6 in Scorpius, and since the ecliptic runs across the feet of Ophiuchus, the Sun spends 19 days there too. On 327 days of 2027, the constellation the Sun is actually in does not share a name with the astrological sign.
Why they are almost a sign apart: precession
Astrology divides the ecliptic into twelve 30° signs counted from the March equinox point; that is a coordinate system. When it was fixed over two thousand years ago, each sign roughly overlapped the constellation of the same name. But Earth's axis wobbles slowly like a spinning top, and the equinox point slides west about 1° every 72 years; over two thousand years it has moved almost 30°. So the astrological sign of Aries now lies mostly in the constellation Pisces.
Western astrology uses this "tropical zodiac" tied to the equinox, which keeps its dates almost the same every year, shifting by a day at most (Aries starts on March 20 or 21, for example); astronomy's constellations are regions fixed to the stars. Neither is wrong; they measure different things.
Why you can't see your sign on your birthday
Around your birthday the Sun is in front of that constellation (or its neighbor), so the constellation rises and sets with the Sun and is drowned in daylight. It rides high at night about six months later. People born from late November into December, for example, see Scorpius and Ophiuchus best on May and June evenings; see the summer sky.
China's twelve stations and the Earthly Branches
Chinese astronomers also cut the ecliptic band into twelve segments, the "twelve stations" (shi'er ci), matched with the twelve Earthly Branches (the branches run in the opposite direction). Jupiter takes about twelve years to go round the sky, crossing one station a year, so it was called the Year Star and used to count years; later a counter-Jupiter, Tai Sui, was imagined moving the opposite way in step with the branches. That is where the idea of "offending Tai Sui" each year comes from; see the 2027 Ding Wei year.
| Station | Branch | Mansions it roughly covers |
|---|---|---|
| 星紀 Xingji | Chou | Dou, Niu |
| 玄枵 Xuanxiao | Zi | Nü, Xu, Wei |
| 娵訾 Juzi | Hai | Shi, Bi |
| 降婁 Jianglou | Xu | Kui, Lou |
| 大梁 Daliang | You | Wei, Mao, Bi |
| 實沈 Shichen | Shen | Zi, Shen |
| 鶉首 Chunshou | Wei | Jing, Gui |
| 鶉火 Chunhuo | Wu | Liu, Xing, Zhang |
| 鶉尾 Chunwei | Si | Yi, Zhen |
| 壽星 Shouxing | Chen | Jiao, Kang |
| 大火 Dahuo | Mao | Di, Fang, Xin |
| 析木 Ximu | Yin | Wei, Ji |
Station boundaries usually fall in the middle of mansions, so only the rough span is listed; sources differ slightly.
Three common misconceptions
With Ophiuchus added, everyone's sign changes.
Astrology's twelve signs are a coordinate system of 30° segments counted from the equinox, never based on the constellations themselves. Astronomy saying the Sun passes through Ophiuchus does not change how astrology calculates.
The twelve zodiac constellations are the same size.
The real constellations vary a lot: the Sun spends 45 days in Virgo and only 6 in Scorpius. Only astrology's signs are an even 30° each.
Sign dates are the same every year.
The dates on which the Sun changes sign shift by about a day from year to year, because the moment it reaches each 30° mark varies. If you were born on a cusp, check that year's actual changeover time.
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.
The solar terms also track the Sun
The 24 solar terms mark every 15° of the Sun's path along the ecliptic, and a BaZi month pillar changes at the solar terms. Enter your birth date to see your Four Pillars.
Zodiac constellations FAQ
How many constellations are on the ecliptic?
By the IAU boundaries the Sun passes through thirteen in a year: the twelve zodiac constellations plus Ophiuchus.
Is Ophiuchus the thirteenth sign?
The Sun crosses Ophiuchus from about Nov 30 to Dec 18 (2027 figures). But astrology's twelve signs are a separate coordinate system counted from the equinox, and they don't gain a thirteenth.
Why don't astrology signs match the constellations?
Precession. The equinox point slides west about 1° every 72 years, almost 30° over two thousand years, so astrology's signs and the constellations of the same name are now almost a sign apart.
What are the twelve stations?
The twelve segments into which ancient Chinese astronomers divided the ecliptic band, such as Xingji, Xuanxiao and Juzi, matched with the twelve Earthly Branches and once used to track the Year Star (Jupiter) and count years.