Nasa thirteenth signAbout five years ago it was discovered that because of the shifting of the Earth’s axis, the constellation Ophiuchus was now closer to the apparent path of the Sun as we observe it from Earth, and astronomers conjectured that this then made Ophiuchus a thirteenth sign in the zodiac.

This popped up recently as “news:”  NASA had changed the system of the zodiac to incorporate the thirteenth sign.

It’s not news the zodiac that we use in Western astrology does not line up with the current placement of the constellations.  This is due to what is called “precession,” in which due to the earth’s wobble the relationship between the earth and the stars changes over a “Great Cycle” of 26,000 years.  This is why every 2160 years or so we go through another zodiacal age, like the transition from the Age of Pisces to the Age of Aquarius that we are in right now.

You can read more about the science of precession here.

The astrological pantheon that we call the zodiac is a symbolic system.  The constellations do not align into nicely divided 30 degree sections as they do around the birthchart, and as many of these news articles mention there is a 13th constellation that the Sun passes through on its trip around the Sun called Ophiuchus.  This last idea has given rise to the question about whether the zodiac should have 13 signs rather than 12.  These are concepts that for many years have caused astronomers to dispute the validity of astrology.

Astrology is not astronomically correct.  Planets don’t really move backwards, and the earth isn’t the center of the solar system.  But that is how we observe the planets astrologically, and we observe them against a backdrop of symbols that are named after the constellations that form the backdrop of our observed world.

In the tropical zodiac, the cardinal points line up with the changing of the seasons.  This is true in the northern hemisphere AND the southern hemisphere, although the seasons of course are reversed in the southern hemisphere.  For example, zero degrees Aries marks the Vernal Equinox in the tropical system, and zero degrees Libra is at the Autumnal Equinox.  In my work with clients in the southern hemisphere, despite the fact that Aries is actually the Autumn season, Aries works exactly the same way, and so does Libra.

As we practice it in the West, astrology is a symbolic system largely credited to the work of Ptolemy whose “Tetrabiblos” was written about 300 years after the phenomenon of precession was discovered, but when the zero degree Aries point was still aligned with the Vernal Equinox according to Rob Hand’s excellent article.  Rob also points out that there is evidence from translations of other works that the Tropical zodiac was favored by the Greeks back to the fourth century bce.

Still, it was nice to see astrology treated with some respect in the mainstream news!


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