What Is a Constellation?

Abstract

From a dark location on Earth, far from sources of artificial light pollution, a few thousand stars are sufficiently bright to be seen by the unaided human eye. One popular misconception about the stars is that brightness indicates distance, fainter stars being located further away from Earth than the bright ones; were it the case that all stars had identical intrinsic brightnesses, this would be true. But by the twentieth century, astronomers realized that the luminosities of stars spanned an enormous range of values, from those many thousands of times intrinsically brighter than the Sun to those just a fraction of a percent of our own star’s luminosity. The brightness of stars, then, does not tell us much about the immediate volume of space we inhabit. That some stars are brighter and others are fainter is also only part of the story by which certain ones come to form recognizable patterns to humans.

[A]ncient customs are difficult to overcome, and it is very probable, that, except the recently-named groups, which we may now suppress, the venerable constellations will always reign.

Camille Flammarion, Astronomie Populaire (1880)