The Sun passes in front of thirteen constellations during the year, not twelve. The thirteenth is Ophiuchus, the Serpent Bearer, and the Sun crosses it from about 30 November to 17 December.

That is an astronomical fact, and it is the reason this question keeps coming back every few years. What it means for astrology is a different question, and the honest answer is: it depends on which zodiac you use.

I am going to keep the astronomy and the astrology in separate boxes in this post, because most of the confusion online comes from mixing them.

The astronomy: where Ophiuchus sits

Ophiuchus is a large constellation between Scorpius and Sagittarius. The path the Sun appears to follow across the sky through the year is called the ecliptic, and it runs through the lower part of Ophiuchus. You can see this on the drawing on our Solar Blueprint page, which is made from real star positions.

The constellations along the ecliptic are very different sizes. In the constellation table I use, the Sun spends only about six days in front of Scorpius and more than six weeks in front of Virgo. Ophiuchus falls in between, at a little over two weeks. Sources disagree by a day or so on the exact dates (EarthSky gives 30 November to 18 December), because the boundaries are lines on the sky and the Sun's timing shifts slightly from year to year with the leap-year cycle.

The lines themselves were drawn by the International Astronomical Union. In 1922 the IAU adopted a list of 88 official constellations, and in 1930 the Belgian astronomer Eugène Delporte drew the boundaries between them. I go through that history in the 1930 constellation boundaries.

The astrology: why most systems use twelve signs

Western astrology usually uses the tropical zodiac. It splits the ecliptic into twelve equal parts of 30 degrees, starting at the point where the Sun stands on the March equinox. Those parts are named after constellations, but they are measured from the seasons, not from the stars. Twelve equal parts fit a calendar neatly, which is one reason the system stayed at twelve.

So the tropical signs and the constellations are two different things that share names. Your tropical Sun sign was never a claim about which constellation the Sun stood in. That is also why the two have drifted apart over the centuries, a story told in why the zodiac drifted.

Did NASA add a new sign?

No. In 2011, and again in later years, a story spread saying NASA had changed the zodiac and added a thirteenth sign. NASA had not changed anything. It had only said, as astronomers always have, that the Sun crosses thirteen constellations. TIME covered the mix-up and the story keeps resurfacing because it is a satisfying one to share.

Who does use Ophiuchus

Some astrologers use a 13-sign sidereal approach. They place each planet in the constellation it actually stands in, at the real, unequal widths of the constellations, and that includes Ophiuchus. In this system, if you were born between about 30 November and 17 December, your Sun sits in Ophiuchus.

I explain the method properly in what the 13-sign zodiac is and how it works. It is a minority approach, and I am not going to pretend otherwise.

What Ophiuchus stands for

In the Greek tradition the figure is linked with Asclepius, the healer who carried a serpent. The staff with a single snake that is still used as a symbol of medicine comes from the same story. Astrologers who use the sign tend to write about it as the integrator: someone who holds two things that seem to pull apart. That is symbolism, not measurement, and you are free to take it or leave it.

Common questions

Is my Sun sign wrong? No. Your tropical sign answers one question (where you were in the yearly cycle of the seasons) and your constellation answers another (where the Sun stood against the stars). They are not competing.

Did the zodiac "move"? The sky did not change its rules. The slow wobble of Earth's axis moved the seasons against the stars over centuries.

Is Ophiuchus a "real" sign? It is a real constellation. Whether it counts as a sign depends on the tradition you are using.

The honest bit

Astrology is not science. It is a way of reflecting on how you work, and every zodiac is a choice of map. None of them is the true one, and I try never to frame one as such. If Ophiuchus feels like it describes you, that is a fine reason to read about it. If you prefer twelve signs, that is fine too.

If you want to see where your own Sun and planets fall in each system, my Solar Blueprint reading shows your chart in four skies: Tropical 12, Sidereal 12, Sidereal 13 and Vedic. I write each reading myself with the help of my own tools, and I check every one before it goes out. You can also come and ask questions in the ADHD MindFlow community.

Astrology is a way to reflect, not science, and it does not predict events.

Astrology is a way to reflect, not science, and it does not predict events. Astronomy facts here are checked against the sources linked. Read our sources, commercial disclosure and editorial approach.