The network signature of constellation line figures

In traditional astronomies across the world, groups of stars in the night sky were linked into constellations -- symbolic representations on the celestial sphere, rich in meaning and with practical roles. In some cultures, constellations are represented as line or connect-the-dot figures, which are spatial networks constrained to the fixed background of stars, but free in their choice of stars and lines. We first define the visual signature of a constellation: a rich, multi-dimensional complexity metric capturing network, spatial, and brightness features. We then answer the questions: are cultures, types of culture, or sky regions strongly associated with the visual signature of their line figures, and thus may have determined their shape? We analyse 1591 line figures from 50 astronomical cultures spanning all continents and a long history, find that the line figures form seven distinct clusters by their closeness in visual signature, and draw the following conclusions. Few individual cultures have unique visual signatures. Oral astronomies are diverse in network and spatial features but use brighter stars. Constellations used for navigation, religious divination, and agrarian/hunter-gatherer time-keeping are similar, but constellations from Chinese and Mesopotamian ancestries have a distinct visual signature. We find clear clusters of cross-culture similarity, with SE Asian traditions far apart from Mesopotamian, N and S American, Austronesian and Polynesian traditions. We also find broad visual signatures in many sky regions: there are diverse line designs around the majority of widely used stars.