Astroblog: A Storm in a Zodiacal Teacup

Sunday, January 16, 2011

A Storm in a Zodiacal Teacup

The Sun in the constellation Ophiuchus on December 12.

A recent article by astronomer Parke Kunkle has had the twitterverse and astrologers in an uproar by pointing out that Sun no longer enters the constellations associated with the zodiac due to precession of the equinoxes.

Tropical Astrologers are boasting that Kunkle is wrong, and their system is better than that of Sidereal Astrologers, because their constellations are defined by the Vernal Equinox, and yar-boo-sucks to those silly astronomers.

However, in Tropical Astrology the zodiacal sign Aries (the Ram) actually points to the constellation we call Pisces. Now, most people couldn't find their own constellation in the sky, but I'm sure they would be perplexed to know that Astrological Aries is the constellation known to and ourselves and the ancient Greeks as Pisces (also, the vast majority of horoscopes that people are familiar with are Sun Sign horoscopes which Tropical Astrologers look down on in the first place). So Parke Kunkle is correct, the Zodiacal signs most westerners are familiar with are not associated with the constellations they are named after.

Yes, zodiacal constellations and actual constellations are two entirely different things. The astrological signs of the zodiac may bear the same names as modern constellations but have little correspondence to either modern constellations or constellations as ancients such as Ptolemy knew them. Both Astrological Tropical and Sidereal zodiacal signs are sections of the sky 30 degrees long and 14 degrees wide, centred on the Suns path. No matter how big or small the actual constellation, the sign associated with that constellation is one twelfth of the length of the Suns yearly journey. Again, we will pass silently over the fact that the tropical zodiac signs are named for constellations that no longer reside in their 30 degree swath due to precession of the equinoxes.

The other thing exercising the astrologers is whether Ophiuchus should be part of the zodiac. Now, boundaries for the astronomical constellations have varied quite a bit since the time of Ptolemy (whose astronomical constellations had very different boundaries to the zodiacal constellations) , but both the modern constellation of Ophiuchus and the ancient Greek one defined by Ptolemy had Ophiuchus crossing the ecliptic, as do all the other constellations of the Zodiac. Now we have an astrologer fulminating:

"This is an old hoax. Historically, Ophiuchus has never been listed as a constellation in the sidereal zodiac. It is a constellation out there, but it’s off the ecliptic (that is, it’s not along the path of the Sun through the sky). I’ve read that Ptolemy mentions it in his literature as an off-zodiac constellation, meaning that the Sun never travels through it...."

Sorry mate, the Sun does travel through it (and has done so since Ptolemy described it back around 100 AD, and probably even earlier based on the Farnese Atlas see the image above), as does the Moon and planets, in fact the Sun spends more time in Ophiuchus than it does in Scorpius. It's good that astrologers are so familiar with the sky they get their predictions from.

What's more, several astrologers have suggested that Ophiuchus should be incorporated into the zodiac (see here, here and here). So I wouldn't call the proposal for Ophiuchus to be a Zodiacal constellation a "hoax", Mr. Astrologer.

Labels: astrology, scepticism, science, zodiac