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Is there a 13th star sign?

This article is written by a student writer from the Her Campus at MSU chapter.

Did you know that your astrological star sign might not actually be your scientific zodiac sign? There’s actually a 13th zodiac constellation that is often forgotten – Ophiuchus, translated in English to ‘the Serpent Bearer.’ Explore the scientific zodiac, and discover how your zodiac sign according to astronomy may be different from the one given to you by astrology. 

What is the zodiac? 

As the Earth rotates around the Sun, we see the Sun’s position change in our sky, for while the Sun isn’t actually moving, our revolutions cause the Sun to appear in different locations in the sky. The position of the Sun follows a predictable pattern, since we stay in the same orbital plane every year. They discovered that the Sun travels “through” 13 different constellations in the sky over the course of a year: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, Capricornus, Aquarius, and Pisces. 

If you are familiar with astrology or know your star sign, you may notice that there is one constellation listed in the astronomical zodiac – the one based on the science of astronomy – that isn’t considered in the star signs of astrology.

Ophiuchus, “the Serpent Bearer”

Ophiuchus (pronounced ‘oh-fee-you-kuss’) is the lesser known zodiac sign, since it is not one of the astrological star signs associated with birthdays. 2,000 years ago, there were only 12 constellations in the zodiac. Ophiuchus means the Serpent Bearer and appears to be holding two parts of a large serpent. Because of its position in the sky near the celestial equator, you can see it from both the Northern and Southern hemispheres. 

Constellations vs. Star Signs

The astrological and astronomical zodiacs are different because they are based on different things. While the Sun moves through 13 constellations over the course of the year, astrological star signs are actually based on 30° sections of the sky. The section the Sun is in throughout the year determines the astrological zodiac sign. Because of this, there are 13 constellations in the astronomical zodiac but 12 star signs in the astrological zodiac. Because of this, Ophiuchus is a constellation, but not an astrological star sign. 

So is there a 13th star sign? The answer is no, because while there are 13 constellations in the astronomical zodiac, astrology doesn’t recognize Ophiuchus as a star sign. 

Date Comparison: Astrological vs. Astronomical Zodiac


Astrological dates = March 21 – April 20

Astronomical dates = April 19 – May 13


Astrological dates = April 21 – May 21

Astronomical dates = May 14 – June 19


Astrological dates = May 22 – June 21

Astronomical dates = June 20 – July 20


Astrological dates = June 22 – July 22

Astronomical dates = July 21 – August 9


Astrological dates = July 23 – August 23

Astronomical dates = August 10 – September 15


Astrological dates = August 24 – September 23

Astronomical dates = September 16 – October 30


Astrological dates = September 24 – October 23

Astronomical dates = October 31 – November 22


Astrological dates = October 24 – November 22

Astronomical dates = November 23 – November 29


Astrological dates = N/A

Astronomical dates = November 30 – December 17


Astrological dates = November 23 – December 21

Astronomical dates = December 18 – January 18


Astrological dates = December 22 – January 20

Astronomical dates = January 19 – February 15


Astrological dates = January 21 – February 19

Astronomical dates = February 16 – March 11


Astrological dates = February 20 – March 20

Astronomical dates = March 12 – April 18

Next time you look up your horoscope, think about what might be different if astrology was actually based on the astronomical zodiac constellations – you might be a different star sign or a constellation separate from the traditional astrology star signs altogether!

Katie is a double major in Journalism and Astrophysics at Michigan State and the Senior Editor for the HCMSU chapter. She is an avid reader and loves writing, especially poetry. When she isn't writing or learning about space, she loves to listen to music and scrapbook. To see some of her recent works, visit her blog: katietswritingcorner.wordpress.com