- A group of stars seen as forming a figure or design in the sky, especially one of 88 officially recognized groups, many of which are based on mythological traditions from ancient Greek and Middle Eastern civilizations.
- An area of the sky occupied by one of the 88 recognized constellations. These irregularly defined areas completely fill the celestial sphere and divide it into nonoverlapping sections used in describing the location of celestial objects.
A Closer Look Various cultures throughout history have chosen different groups of stars in the night sky to form different constellations. While it was once thought that the Greeks were responsible for determining many of the constellations known today, it is now believed that the mythological origins of the 48 ancient constellations predate the Greeks and originate instead from ancient Middle Eastern civilizations. In the seventeenth and eighteenth centuries another 40 constellations were invented by Europeans for navigational purposes. The boundaries of the 88 constellations currently recognized were defined in the 1920s by the International Astronomical Union. There is no scientific reason why there are exactly 88; the modern constellations are only a convenient way to break up the sky to locate the position of celestial objects or track satellites. Although the stars in any given constellation may look like they're neighbors, they can actually be many light-years apart, and if seen from another part of the galaxy they would form different groups and shapes altogether. Constellation names are usually given in Latin, such as Ursa Major (Great Bear) or Centaurus (Centaur),
and individual stars in constellations are named in order of brightness, using the Greek alphabet, with the genitive case of the constellation following. Therefore, Alpha Centauri is the brightest star in the constellation Centaurus, Beta Centauri is the second brightest star, and so on. The stars within our galaxy are rushing through space in various directions, and as the millennia pass, the arrangements of the star groups as seen from Earth will change, inevitably altering the constellations as we know them.