Constellations are patterns of stars as seen from Earth. Ancient civilizations used these star patterns for navigation, timekeeping, and storytelling. Different cultures developed different constellation systems, which led to the need for standardized classification that we use today.
Throughout history, different cultures developed their own constellation systems. The Greeks and Romans created 48 classical constellations that form the basis of our modern system. The Chinese developed the Three Enclosures and Twenty-Eight Mansions system. Arabic astronomers contributed many star names we still use today. Indigenous cultures worldwide created their own meaningful star patterns for storytelling and navigation.
In 1922, the International Astronomical Union standardized constellation classification, establishing 88 official constellations with precisely defined boundaries using coordinate systems. This created scientific uniformity, distinguishing between asterisms, which are star patterns, and constellation areas, which are defined regions of sky. This system ensures that every point in the sky belongs to exactly one constellation.
Constellations are classified by their sky regions. The Northern Hemisphere contains 29 constellations, while the Southern Hemisphere has 47. The equatorial region includes the 12 zodiacal constellations plus others. Some constellations are circumpolar, meaning they're always visible from certain latitudes, while others show seasonal visibility as Earth orbits the Sun.
Constellations can be classified by their historical origins and types. By origin, we have 48 ancient Ptolemaic constellations, Renaissance additions mainly from southern sky discoveries, and modern additions that filled remaining gaps. By type, we distinguish zodiacal constellations, large versus small constellations, and bright versus faint ones, each serving different astronomical and cultural purposes.