Ophiuchus: is there a 13th zodiac sign?

No, there is no 13th zodiac sign, and your sign did not change. Ophiuchus, the Serpent Bearer, is a real constellation, and the Sun passes in front of it roughly from the end of November to mid-December. But zodiac signs are not constellations. They are twelve equal sections of the sky, and there have always been exactly twelve of them.

What is true about Ophiuchus

The story of a 13th sign comes back every few years as a headline. It rests on facts that are correct, and on one mix-up.

The correct part:

• Ophiuchus exists. It is a large constellation, a figure holding a snake, and it lies between Scorpius and Sagittarius.
• The Sun passes in front of it. Seen from Earth, the Sun moves along the same path through the stars every year. Roughly from the end of November to mid-December, the stars behind it belong to Ophiuchus.
• There are 13 constellations on the Sun's path. Astronomers count 88 official constellations in the whole sky. Thirteen of them lie on the Sun's path: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, Capricornus, Aquarius and Pisces.

The mix-up: the story treats constellations and zodiac signs as the same thing. They are not. None of this is new, either. Ophiuchus was already known as a constellation in antiquity, and the zodiac of twelve signs has been in use for more than two thousand years.

Constellations and zodiac signs are two different things

A constellation is a pattern of stars with a border around it. The patterns have very different sizes, and their borders are a convention of astronomers. On its yearly path the Sun takes several times longer to cross the wide constellation Virgo than to cross the short stretch of Scorpius.

A zodiac sign is a unit of measurement. The circle of the Sun's path has 360 degrees, and the zodiac divides it into twelve equal sections of 30 degrees. In Western astrology the count starts at the March equinox, the moment around March 20 or 21 when day and night are about equally long. The first 30 degrees are called Aries, the next 30 Taurus, and so on.

The signs took their names from twelve of the constellations. That is where the confusion starts. A name is not a border.

A constellation is a picture made of stars. A zodiac sign is a step on a scale. The Sun can stand in both at once.

Why your zodiac sign did not change

"Your sign" means your Sun sign: the section of the zodiac the Sun stood in when you were born. It depends on the scale, not on the star pattern behind the Sun.

Take someone born in early December. The Sun enters the sign Sagittarius around November 22 and leaves it around December 21. The exact day shifts by a day depending on the year and on your time zone. In early December the Sun stands in the middle of that section. This person's Sun sign is Sagittarius. At the same time, the stars behind the Sun belong to Ophiuchus. Both statements are true. They answer different questions. What the sign Sagittarius is like

Three reasons why the scale has twelve steps and stays that way:

1. A scale needs equal units. The Sun moves about one degree per day. Twelve signs of 30 degrees give it about 30 days per sign. A ruler with thirteen steps of different lengths would be hard to measure with.
2. The twelve were a choice, not an oversight. The zodiac was built as a scale of twelve equal parts. It was never meant as a list of every constellation the Sun crosses.
3. The signs do not sit on their constellations anyway. The zodiac of Western astrology is tied to the seasons, not to the stars. Because Earth's axis wobbles slowly, the two have drifted apart by about 24 degrees. Vedic astrology uses a zodiac tied to the stars, and that one has twelve equal signs as well. How the tropical and the sidereal zodiac differ

So the full list of zodiac sign dates is the same as before. The only people who need to look closer are those born on a day when the Sun changes signs. For them the birth time decides.

What about Ophiuchus personality traits?

You can find lists of "Ophiuchus traits" online. They have no tradition behind them. In astrology, the meaning of a sign has grown over many centuries, together with its element, its mode and its ruling planet. Ophiuchus has none of these, because it was never part of the system.

There is also nothing you would gain. Astrology describes tendencies, and it does so through a whole chart: the Sun sign, the Moon sign, the Rising sign (also called the Ascendant) and the planets. One more Sun sign would not make the picture more exact. More of your own chart does. How Sun, Moon and Rising work together

Why the 13th sign story keeps coming back

The story works because both halves sound like science. Astronomy does say that the Sun crosses thirteen constellations. Astrology does use the names of twelve of them. Put side by side without explanation, it looks as if someone miscounted.

Nobody did. Astronomy describes what is in the sky. Astrology is a symbolic language that uses a twelve-part scale to name positions. The two are counting different things. How astrology differs from astronomy

What to do next with your own chart

1. Keep your sign. If you know your Sun sign, it is still your Sun sign.
2. If you were born on a day when the Sun changes signs, look up your birth time and have the exact position calculated.
3. Then go one step further than the Sun sign. Your Moon sign and your Rising sign add more to the picture than a thirteenth constellation ever could.