About 4500 years ago early civilizations in China, Egypt and the Middle East began to divide the sky into groups of constellations – arbitrary formations of stars that are perceived as figures or designs – which were named in various ways. The Chinese had one method, the Egyptians another, but the one we follow today is based on that of the ancient Greeks, although it actually originated around 4000 years ago with the Sumerian people.
The Greeks named the constellations after their gods, heroes, fabled animals, or objects that had special associations with the gods. Orion is a hunter, Draco is a dragon, Hercules is a warrior and Andromeda is a princess, daughter of king Cepheus. With some exceptions – among them Orion, Scorpius, Gemini, and Taurus – few constellations look like the animal or person they are named after, and you should not be frustrated if you cannot see a princess or dragon in the night sky. In fact, a constellation pattern has no real significance, because the stars that form the constellation have no physical relationship to one another and are many light years apart.
By the time of the Greek astronomer Ptolemy in A.D. 150, 48 constellations were recognized, including the 12 constellations of the zodiac through which the Sun passes on its yearly path around the sky. Since then, various other constellations where added, especially in the far southern part of the sky that was invisible to the Greeks. Most of them have modern-sounding names such as Microscopium (the Microscope) and Horologium (the Clock).
Some of the newly invented constellations have since been abandoned, and those that remained frequently overlapped one another or shared the same stars. Finally, in 1928, the International Astronomical Union, astronomy’s governing body, put matters on a more systematic footing. They adopted the list of 88 constellations we know today, and set down their rigorous boundaries.
Detailed information about a particular constellation can be found by clicking on its name in the list below. This information covers data and descriptions about stars, deep sky objects, and meteor showers. The maps show stars down to magnitude 6.5, and deep sky objects visible in small telescopes.