Ophiuchus- the 13th Sign of the Zodiac

Ophiuchus holds a huge snake, Serpens, in both hands as shown in the Atlas Coelestis of John Flamsteed. 

If asked, most people can tell you what their “sign” is. They’ll tell you Gemini or Scorpio, or if you ask me- ‘Caution: rough road ahead.’ Few people actually know what it means though. Their ‘sign’ is actually their ‘sun sign’, the constellation of the Zodiac the Sun appears to reside in at the moment of their birth.

The truth is, that special solar alignment with the stars might have been true 2600 years ago, when Babylonian astrologers started making this stuff up, but it isn’t true any more.

First, the dates the Sun spends in each constellation each year have shifted by a few weeks. The Sun's 21st century position against the background stars has shifted by as much as two constellations from its position noted by astrologers in the 5th century B.C. In their time, the Sun was in front of the stars of Gemini during the first two weeks of May. Now the Sun is in front of the stars of Aries during the same two weeks. So what happened?

The earth’s axis, the imaginary line you draw from the south pole to the north pole, around which the earth rotates, is wobbling very slowly over time; like a top that is slowing down. This wobbling is called precession, and it's so slow that the earth takes 25,800 years to complete one wobble. During this time, the positions of stars as measured in the equatorial coordinate system slowly change. This change is due to the change of the coordinates caused by precession, not the motion of the stars themselves. 

The affect it has on the measured positions of the stars is called “precession of the equinoxes”. Over time, the position of the Sun on the first day of spring, the vernal equinox, slowly drifts around the sky. Five thousand years ago the Sun was in Taurus, near the Pleiades star cluster, on the first day of spring. Now the Sun is in the constellation Pisces. Six hundred years from now the sun will be in Aquarius as spring begins. This will of course signal the beginning of the fabled Age of Aquarius, a time of universal peace and brotherhood (if you believe in that sort of thing).

So the constellations have stayed in the same place in relation to each other, but the signs associated with astrology have drifted to the west, and they no longer coincide. If we go back to our person born in the first two weeks of March; astrologically speaking he is a Taurus; astronomically speaking he is an Aries. The Sun is actually in Virgo for people supposedly born under the sign of Libra, Gemini is now Taurus and so on.  Yes, astrology is built on some pretty shaky, constantly changing ground.

Even more interesting is the fact that the Sun actually resides in the constellation Ophiuchus for a good piece of the year, yet there is no astrological sign for Ophiuchus. Yes, children, there should be a thirteenth astrological sun sign, Ophiuchus.

How did this great injustice happen, and what is an Ophiuchus?

When the astrological sun sign system was set up more than two thousand years ago, the sun's path was divided into twelve equally spaced "signs," each 30 degrees wide. The full 360 degrees around the sky divides up quite nicely into 12 equal parts of 30 degrees. The stars aren’t quite so conveniently arranged. These signs have never lined up very well with the actual constellations in the sky. For one thing, they are all of various sizes and shapes. Virgo is the second largest constellation in the sky as measured in square degrees, yet Cancer, coming in at 31st largest, gets the same area according to astrology.

Worse yet, every astronomer and astrologer had his own idea of where the constellations began and ended, and even how many constellations there were. Everyone who drew a star atlas had a different version of the picture associated with the constellation and which stars belonged to which constellations. The constellation Libra was arbitrarily created by cutting off poor Scorpio’s claws to help round out the astrological need for twelve signs. Constellations aren’t real. People made them up, created great stories and legends associated with the characters, and passed them down through the ages as part of their culture.

Legends and ambiguity may be fine for astrologers and folklore, but scientists need more specifics. Astronomers finally brought order to the confusion when the International Astronomical Union set the official constellation boundaries in 1930.  Each constellation was published as a set of specifications that reads like a surveyor's plot of irregular parcels of land. 

This redrawing of the boundaries added a constellation to the Zodiac. The Zodiac, the constellations that lie on the plane of the ecliptic through which the Sun passes in the course of a year, now has 13 constellations, not 12. This thirteenth ‘sun sign’ of the zodiac is Ophiuchus, the Serpent Bearer, and the Sun is in front of its stars during the first half of December. As it turns out, most Sagittarians are really Ophiuchans. Below is a list of constellations and the dates the Sun now appears in front of those stars in the 21st century.

SAGITTARIUS December 19 - January 20
CAPRICORNUS January 21 - February 16
AQUARIUS February 17 - March 13
PISCES March 14 - April 19
ARIES April 20 - May 15
TAURUS May 16 - June 21
GEMINI June 22 - July 21
CANCER July 22 - August 10
LEO August 11 - September 17
VIRGO September 18 - October 31
LIBRA November 1 - November 24
SCORPIUS November 25 - November 30
OPHIUCHUS December 1 - December 18

Astrology is really a mess. It's based on superstitious beliefs regarding the apparent path of the Sun and planets against the background of stars, divided into constellations of fictitious beasts, monsters and legends, which no longer line up with the Sun’s position on those dates, and was made up by ancient people who thought the earth was flat. It doesn't have anything remotely to do with your personality or fate.

The Babylonians chiseled their predictions of planetary motions into stone. (British Museum) 
We've made a little progress since then. Who are you gonna believe?

So, who is this Ophiuchus anyway? The Greeks knew him as Asclepius, the god of medicine. Asclepius was the son of Apollo and Coronis. Coronis was the goddess of Mexican beer. Not really, just kidding.

According to legend, Coronis was an unfaithful wife to Apollo and slept with a mortal, Ischys, while she was pregnant by Apollo. A crow brought Apollo the unwelcome news, but instead of being rewarded, the raven, which until then had been snow-white, was cursed by Apollo and turned black and lost his voice. This crow or raven is also immortalized in the sky as the constellation Corvus.

In a typical Greek god fit of rage and jealousy, Apollo shot Coronis with an arrow, but rather than see his unborn child perish with her, Apollo snatched the unborn son from his mother’s womb just as the flames of the funeral pyre engulfed her, and took the infant to Chiron, the wise centaur, also represented in the sky by the constellation Centaurus. The centaur raised Asclepius as his own, teaching him the arts of healing and hunting. Asclepius became so skilled in medicine that not only could he save lives; he could raise the dead.


Raising people from the dead is the line in the sand I draw between fiction and fact. And that is why when people ask me what my “sign” is, I tell them ‘Caution; rough road ahead’ or STOP!

The brownish-red dashed line is the path of the ecliptic. As you can see, 
it just barely passes through Scorpio, but cuts through Ophiuchus a great deal.

If you happen to be a proud Ophiuchan, your constellation has some things that actually exist in the sky, whose astronomical splendor you can observe throughout the late spring and summer. First of all it contains seven Messier globular clusters- M9, M10, M12, M14, M19, M62 and M107- making Ophiuchus pretty much the king of globular clusters. Also, NGC 6240, the strange remnant of a merger between two smaller galaxies, resulting in a single larger galaxy, with two distinct nuclei and a highly disturbed structure. The high proper motion star and one of the closest stars to the Sun, Barnard’s Star can be found in Ophiuchus, as well as RS Ophiuchi, a recurrent nova thought to be teetering on the brink of becoming a Type 1A supernova. 

NGC 6240 in Ophiuchus. Credit: NASA/ESA

It’s fun to learn the meaning and the legends behind all the astronomical names, made up by people thousands of years ago as they looked to the sky in amazement at celestial patterns and motions they didn’t understand.  But it’s a lot more fun to observe the heavens through the eyes of a 21st century critically thinking human being, capable of understanding to a great extent, the origin, history and fate of our universe. The universe is beautiful, amazing and mysterious without the mumbo-jumbo. 


Sakib said...

Ah this post brings back happy memories of when I first got interested in astronomy almost 15 years ago. I remember reading about precession when I was 11 and I honestly couldn't believe that Thuban was the pole star 3000 years ago! I've often thought that Ophiuchus was excluded from the zodiac as grave misfortune and bad luck was associated with the dreaded number of 13. It is really fun reading about the myths and legends associated with the constellations, particularly the Ptolemaic ones. Quite a lot of the most recently formed constellations don't include an interesting backstory, I guess it is difficult to create a legend about constellations that represent microscopes and clocks!
Also some of the ancient Greek astronomers surely were aware of the yearly motion of the stars? I've kinda forgotten my ancient astronomical history so I'm probably wrong!
Also a really cool object in Ophiuchus is the dark nebula LDN 43.

Sean said...


So I'm not really an "Aquarius", but a Capricorn... not that it really means anything anyway.

ericl1 said...

I read somewhere that Cetus was also in the zodiac.

Anonymous said...

Really, it just gets worse, it really does.

Astronomy, for in past times it was basically interchangeable with astrology, used to use an ecliptic coordinate system. Not the modern ecliptic coordinate system either.

In one of its oldest forms the sky was separated into 12 Houses of the Zodiac, each 30 degrees, irrespective of modern day constellation boundaries.

The positions of stars were expressed as their altitude (probably at which time, I forget the details) and which House they were in. All stars were placed this way, even if they weren't in the Zodiac "proper" or on the ecliptic.

Yes, precession has moved the First Point of Aries to the First Point of Pisces, and soon enough to the First Point of Aquarius, but the zonal 12 Zodical Houses were 30 degrees each, irrespective of which asterisms they crossed, and irrespective of modern day IAU constellation boundaries.

"Not even wrong" is drowning the hobby of astronomy more and more every day. Debunking something with misinformation only leads to debunking the message too.

Gordon Bennett

georgi said...

Nice beer joke!

Andy Fleming said...

With a glint in my eye, I always wind people up who ask for my horoscope sign... I always answer Ophiucan! They either change the subject with a funny look... or we engage in a conversation about how the gravity of Mars or Saturn cannot possibly affect their everyday lives...!

Amazing the lead-ins for astronomy outreach!!!

Gilly said...

Ophiuchus is totally cool being the thirteenth astrological sign of the zodiac AND he was actually a MAN!

I'm not surprised he was highly intelligent, wore flamboyant clothes and was good at handling snakes. I was once going to study to become a lawyer (lol!).

@CDANKK said...

I want to know my traits being a Ophiuchus ,, since I am no longer a Saggitarius.. lol I think i'll keep reading my Saggitarius horoscope until horoscopes get a phenominal change.. that will adjust into the lives of everyone :) in the meantime FOLLOW @CDANKK

OLO said...

-giggle- that's really interesting... I always looked down on people who believed in astrology until a few months ago when my friend showed me my profile (Sagittarius) on this site and I am not joking one bit EVERY SINGLE word fit me to a tee ... it was really long and detailed too, and when I clicked on the other profiles thinking maybe they're all just generalisations and all the profiles could fit anybody if you wanted to believe in it... but none of the other profiles matched me as neatly as Sag. My friend.. the one who showed me.. is a Cancerian and her profile matched her EXACTLY as well... now I don't know what to think about astrology... on the one hand - looking at it with a scientific, rational point of view (like this) it really sounds like a load of crap but at the same time... it's SCARY how much Sagittarius fits me so well!! Maybe there's a logical explanation lol... ppl born in certain times of year due to environmental factors will be more inclined to be lazy/optimistic/selfish rofl Idk but it's really weird how true that stuff is... for me personally, anyway.

Teri said...

As someone who studies the history of astronomy AND astrology from Antiquity up through the Middle Ages, I have to take issue with your rather derogatory attitude toward the ancients. I would love to see you or any other modern scientist sit down with the instruments Ptolemy had to hand and write a set of planetary positions as mathematically accurate as he did in the Almagest. I would also like to see you be able to cast a horoscope, a real one, not these stupid modern newspaper things. A real mathematical horoscope using only the astronomical tables and an astrolabe.

Now before you write me off as a quack, I don't believe in astrology. I don't think the Earth is the center of the universe, and I'm well aware of the modern discoveries in astronomy (on the NASA and JPL mailing lists, thank you very much). However, I also am able to appreciate what the ancients did, what they were able to do and how intelligent they were.

You also have a glaring fallacy in your post here...which was the reason I was initially wanting to comment. People in Antiquity, in the Middle Ages, in the Renaissance did NOT believe the Earth was flat! This is a myth that was started in the 19th century and has been believed and taught in schools ever since. It is NOT true. Sure, probably some people believed it, but the majority, particularly the educated people whose texts we have believed in the Aristotelian system, i.e. the universe is a sphere, from the sphere of the fixed stars on down to the sphere of the earth. Yes, that's right. The earth is a sphere in Aristotelian cosmology. ...and no, the Catholic Church did not take issue with that. They believed that as well. Their issues with Aristotle involve other cosmological and religious problems like that of creation.

And for Sakib, yes, the ancient astronomers (at least in the Graeco-Roman period) were aware of precession and had measured it to a fairly accurate degree.

karthurexcalibur said...

I'm sorry, but you misinterpret much of the mythos behind the constellations, you seem to be laboring under the delusion that most people nowadays believe that the characters and creatures the stars were named from were actually what they are, when in reality many of them were glorified or demonized men women and earthly creatures that did exist, specifically aesclepius. did it ever occur to you that the whole "raise the dead" bit was in actuality the primitive invention of procedures like CPR and the Heimlich maneuver. all the mythos really mean are that he changed the rules that defined mortality back then, and he did so without scientific proof. the people of that time wished to immortalize his skill and honor him for all time, what better way than to deify him, pop his name on a constellation and give him an adoptive deified daddy. these same type of methods were used on all the Grecian named constellations, be they animal, human, or monster.

Anonymous said...

wel wel aint this something I was born on Dec 13th 1989 my zodiac was sagittarius but now Im the 13th sign that has to do with snakes and my chinese horoscope is snake

Jane said...

So astrology is a myth. Will someone tell me why people in certain signs really do have similar traits, then? And, by the way, does anyone know where I left my keys? Oh, here they are. Right in front of me. Sag(Ophiuchus says)

Anonymous said...

Just because you do not understand how gravity can affect water (considering we are 80% or so water) think of the moon and the tides... even if you won't take it seriously, how can you negate astrology, saying that it is wrong because the sun has shifted (true), but maybe that's why you think its wrong, because others are doing it the old way and not based on current positions. People believe this stuff because it has been tailored to be accurate to the old formula.. whether the formula is right or not, the readings appear to be... so maybe we could look at the real planetary positions, and shift our thinking back to how it does affect us. How can it not? We are pulled by gravity, and are shaken by the vibrations of everything in this universe, whether we feel it or not. They say radio frequency can cause health problems in large quantities, why would other vibrations not have an effect on us? Just because you cant see radio, cell phone, or wifi signals doesn't mean they don't exist... and it doesn't mean they don't affect us.

Pollux said...

Well-written, interesting post!

Lilia said...

Wow, you really need to get over yourself and lighten up.

Ben said...

I believe there is another zodiac to be placed somewhere between Pisces, Aries, & Taurus, they have too many days set out for them...

Anonymous said...

Good info, but it is not accurate to say that people who devised these symbols believed the world was flat. Very few civilizations believed the world was flat, and certainly not any that followed the stars.

Anonymous said...

The old Zodiac horoscope Dates for Sagittarius run from November 22 to December 22. According to the New Zodiac Signs 2011, the dates for Sagittarius are from December 17 to January 2011 as said by Astologist that there are sidereal astrology compatibility or you can read more at http://itwel.com/ophiuchus-2011-new-ziodic-signs-with-13-horoscopes-dates.php

Anonymous said...

Great info.... I do have a question I have gone from a
Scorpio to a Libra and Was I always a Libra or was I acturally both, bc I have felt like the past 8 yrs or so I have switch to a libra... Also my last question is that does anyone know what the new 13th sign color is.

Anonymous said...

Hilarious article !

For those seeking more info on Ophiuchus, I recommend this url: http://www.mynewzodiacsign.net/?page=ophiuchus

Anonymous said...

If the sun enters Ophiuchus first before Sagittarius, then how can Ophiuchus be the 13th sign? Sounds more like it's the 9th sign.

Ana_treek said...

Nice read.. I loved the style, you feed us everything and just when we are about to swallow, you choke it out by telling everything is a lie :)

Anonymous said...

Nice article, realy intersting :)

Anonymous said...

Very interesting article. To mix a couple of topics. Chinese Years. I was born during the year of the snake(earth), my zodiac symbol is now Ophiuchus(snake bearer) and numerology. The year, month and day I was born on add to 2012. Coincidence? And there is only one date where you can have all three of these. 11/12/1989

Anonymous said...

Nice...no wait..this sucks. why? because you're an astronomer trying to use astronomical means on an astrological scale...13 signs has nothing to do with 12 houses. do the simple math first jimmy, its 0-360 vs. 0-30x12. Also, astrologically speaking, Ophiuchus is somewhat esoteric in its influence and true origin, in other words, leave it alone. It's not for you to be considering.......obviously. leave the astrology to an astrologist yea? lets try showing a little respect for things we have yet to consider

Mike Simonsen said...

It still surprises and saddens me that this one piece is the most viewed article on my blog, years after it was written, and the majority of you find it online because you still believe in this baloney. I'm not going to argue with you. I don't take it that seriously. Astrology is for entertainment purposes only.

Anonymous said...

Agreeing with all the posters regarding the flatness of the earth. The simple fact that they are dividing 360 by 12 shows that they were aware of the circular nature. No doubt, that very anciently, it was not understood that seeing a group of stars set beyond the horizon was not "falling to earth" and hours later again rising in the opposite horizon was not "rising from the underworld", but that is how the mythos originated. Thus Set opposed Horus-rizing.