Sky Talk June 2009: The 13th Sign of the Zodiac

The controversy between astronomers and astrologers over the validity of astrology has raged for centuries, the latter claiming it’s factual and the former that’s its pure pseudo-science with no basis in fact. There’s fault on both sides for this situation, with astronomers typically not having the time or patience to explain their position to astrologers — and astrologers ignoring even the most basic facts about the sky. This month offers readers a perfect opportunity to look up and see a glaring example of such neglect.

Astronomers are so opposed to astrology that the Astronomical Society of the Pacific has created an “Astrology Defense Kit” for the use of its members. Among other things, it contains Ten Embarrassing Questions for astrologers, which sums up arguments against the practice. (To view it, go to and enter “Astrology Defense Kit” in the site’s search window.) Astrologers have yet to come up with their own version of this directed at astronomers. An entire book could easily be devoted to this controversy. But there is something in June’s sky that provides a striking insight into it — something that supports the position taken by astronomers.

Most of us have heard that there are 12 signs or constellations of the zodiac, which lie along the 18 degree-wide ecliptic pathway of the Sun and planets around the sky. And these play a major role in the predictions of astrology. But, in fact, there are actually 13 of them! If you set your Scientific’s Star and Planet Locator (discussed here last month -#30092-27) to about 10 p.m. local time and face south, you’ll see a large dim constellation called Ophiuchus positioned between Scorpius and Sagittarius. This sprawling figure lies squarely on the ecliptic, as shown on the Locator. But I have yet to meet an “Ophiuchian” – have you? Astrologers ignore this constellation, but if your sign is supposedly Scorpius or Sagittarius, you may actually be one instead!

Another big issue related to the zodiac is that of the precession of the equinoxes. Due to the slow 26,000 year cycle of the Earth wobbling on its axis, all of the constellations marking this celestial pathway have shifted westward by one constellation or sign since the system of astrology was originally set up. Thus, if based on your birth date you’re supposedly an Aquarian for example, you are actually a Piscean!

My personal feeling as an astronomer is that the stars provide “psychic anchors” for those astrologers possessing genuine psychic powers — much the same as do crystal balls, Tarot cards and palm reading for others having such abilities. This would explain why in some cases an astrological reading appears to be “right on the money.” But the stars themselves play no actual role in determining your destiny.

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of five books on stargazing.


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