Which constellation do you belong to? Do you know that since these
constellations are located in the Zodiac, the path of the Sun in the sky,
therefore they are collectively called Zodiacal Constellations? On your
birthday, the Sun has just travelled past your constellation. Yet, things
have changed over the past 2,000 years or so.
The celestial phenomenon witnessed now is not
the same as 2,000 years ago. Since the earth's axis actually sweeps out a
cone with a period of about 26,000 years, the position of the Zodiac in the
sky changes accordingly. As a result, the arrival time of the Sun at the
same constellation will be delayed for about one month every 2,000 years or
so. Furthermore, a thirteenth constellation, Ophiuchus, is also in the
Zodiac now. Using the diagram on the left, you can compare the present
constellations the Sun passes by on your birthday with the traditional ones.