Are all zodiac signs constellations: 59 Photos
FAQs
One constellation tradition is the western zodiac, which is made up of 12 constellations: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces.
Bottom line: You might associate the word zodiac with astrology, but it has an honored place in astronomy, too. The zodiac is composed of the 12 constellations that lie along the annual path of the sun across the sky.
Cetus and Perseus are not considered as zodiac constellations because they do not lie along the ecliptic, which is the path the Sun appears to trace across the celestial sphere throughout the year.
The main reason astrological signs fail to line up with the zodiac, though, is a wobble in the Earth's rotational axis called precession. As a result of its rotation, the Earth bulges slightly at the equator, not unlike how a skater's skirt fans out as she spins.
Ophiuchus. Ophiuchus is one of the thirteen constellations that cross the ecliptic. It has sometimes been suggested as the 13th sign of the zodiac. However, this confuses zodiac or astrological signs with constellations.