The round plane of the sky that we see from Earth has been divided into 88 constellations so that we can keep track of the stars belonging to particular celestial regions. Among these ‘countries’ of the sky, 13 are special because the sun travels through them throughout a year. Twelve of these thirteen were known from times immemorial as the signs of zodiac, or ‘rashi’ in Bangla. They were very important in the old practice of astrology.