Good question!
If you look at any star chart, you will see that the narrow path that the planets and the Sun move along, called the Ecliptic, passes through the 12 classical zodiacal constellations, plus it comes within 1/2 degree of the northern corner of Orion, 1/4 degree from the north west corner of Cetus, 1 degree from the north east corner of Sextans, and the entire southern quadrant of Ophiuchus from Ra = 16h 20m to 17h 40m.
The problem is that the constellation boundaries have been redrawn several times in the last 5 centuries. Astronomers don't care, and astrologers only use the classical, ancient definitions of where the zodiacal constellations are located. Ophiuchus would be no doubt an unlucky '13th house' between Sagittarius and Scorpius so it is simply ignored. The sun is in this house between November 30 and December 17 each year. For more on this, have a look at the Griffith Observatory article by John Mosley. Here is his table of the astronomical signs of the zodiac and where the sun is:
Astronomical Constellations of the Zodiac Constellation Dates Capricornus January 19 to February 15 Aquarius February 16 to March 11 Pisces March 12 to April 18 Aries April 19 to May 13 Taurus May 14 to June 19 Gemini June 20 to July 20 Cancer July 21 to August 9 Leo August 10 to September 15 Virgo September 16 to October 30 Libra October 31 to November 22 Scorpius November 23 to November 29 Ophiuchus November 30 to December 17 Sagittarius December 18 to January 18
By the way, the dates that are given for your astrological sun-sign are supposed to indicate when the sun will be in that constellation during the year. In fact, when you think that you are a 'Sagittarius' you are in fact a Capricorn because the Sun is in this constellation during those dates. Astrologers don't care, and no one listens to astronomers when they say that astrology is idiocy masquerading as fact!
Copyright 1997 Dr. Sten Odenwald
Return to Ask the Astronomer.