In ancient times, when people looked up at the sky in the night, they observed many bright stars arranged in a certain pattern or group. Each group is called a constellation. It means a group of stars. Studies of movements of these constellations led to the discovery that they move in space in fixed directions. The number of constellations visible during the year at different times was found to be 12. The Sun and the Moon were always seen rising and setting in the same directions in which these twelve constellations were located. These 12 constellations were called the signs of the zodiac.
The hypothetical part of the sky through which the Sun, the Moon and other planets seem to be passing is called the zodiac. Each of the 12 constellations situated at an angle of 30°, is named as a different sign of the zodiac. In this way the 12 signs of the zodiac have come into existence. Each sign is connected with one constellation and the shape of each constellation resembles certain earthly body or substance. The names of these signs and the position of the Sun are as follows:
- Aries: The Ram – 21 March to 19 April
- Taurus: The Bull – 20 April to 20 May
- Gemini: The Twins – 21 May to 21 June
- Cancer: The Crab – 22 June to 22 July
- Leo: The Lion – 23 July to 22 August
- Virgo: The Virgin – 23 August to 22 September
- Libra: The Balance – 23 September to 23 October
- Scorpio: The Scorpion – 24 October to 21 November
- Sagittarius: The Archer – 22 November to 21 December
- Capricorn: The Goat – 22 December to 19 January
- Aquarius: The Water Bearer – 20 January to 18 February
- Pisces: The Fish – 19 February to 20 March
In other words, these are the 12 constellations through which the Sun appears passing during a year e.g. during 21 March to 19 April, the Sun is supposed to pass through the constellation Aries or Ram; during 20 April to 20 May, through Taurus and so on till it reaches Pisces.
The science of astrology is based on these 12 signs of the zodiac. Astrologers use the dates given above. In addition to these twelve constellations, in the ancient times, people knew of 36 more constellations. Thus, during olden times, people had knowledge of 48 constellations.
Subsequently, astronomers discovered 40 other constellations. Thus, man knows about 88 constellations. The Hydra constellation is the biggest amongst them. This has at least 78 such stars that can be seen without any aid.
