What is a constellation?
Some well-known constellations contain striking and familiar patterns of bright stars. Examples are Orion (containing a figure of a hunter), Leo (containing bright stars outlining the form of a lion), Scorpius (a scorpion), and Crux (a cross).
The International Astronomical Union (IAU) divides the sky into 88 official constellations with exact boundaries, so that every direction or place in the sky belongs within one constellation. In the northern celestial hemisphere, these are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages, and contains the signs of the zodiac. The sun appears to pass through the 12 constellations of the zodiac (plus ...more