Constellation

A constellation is a recognized pattern of stars in the night sky. The word is from the Latin constellacio, meaning a set of stars. There are 88 official constellations. Many are very old. They’re a link between us and our ancestors, a projection of human imagination into the cosmos: ancient people looked at the stars and thought they saw mythical beings, beasts and cultural touchstones among the stars. Stars in a constellation all lie at different distances from the Earth. For example, the three stars comprising the constellation of Triangulum are between 35 and 127 light-years away. While a constellation may look as if all of its stars are the same distance away, in reality that is only because, as we now know, stars vary in size and brightness, so two stars which appear to be the same brightness in the sky may actually be separated by vast distances. This means that an alien astronomer on a planet a hundred light years from Earth would know very different constellations, because they would see the night sky from a completely different perspective.