Constellations in the far southern sky were added from the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere. They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin probably predates these works by several centuries.

The 48 traditional Western constellations are Greek. Some were limited to a single culture or nation. Some became popular, only to drop into obscurity.

The recognition of constellations has changed significantly over time. Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. People used them to relate stories of their beliefs, experiences, creation, or mythology. The origins of the earliest constellations likely go back to prehistory.

Bottom: Contemporary map of Orion from the IAU and photograph of the night sky with drawn linesĪ constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.

Top: Baroque drawing of the constellation Orion from Johannes Hevelius ' Celestial catalogue, showing the stars as they would appear to an observer looking down upon the imaginary celestial sphere from the outside.

The constellation cassiopeia