  In traditional astronomies across the world, groups of stars in the night sky
were linked into constellations -- symbolic representations rich in meaning and
with practical roles. In some sky cultures, constellations are represented as
line (or connect-the-dot) figures, which are spatial networks drawn over the
fixed background of stars. We analyse 1802 line figures from 56 sky cultures
spanning all continents, in terms of their network, spatial, and brightness
features, and ask what associations exist between these visual features and
culture type or sky region. First, an embedded map of constellations is learnt,
to show clusters of line figures. We then form the network of constellations
(as linked by their similarity), to study how similar cultures are by computing
their assortativity (or homophily) over the network. Finally, we measure the
diversity (or entropy) index for the set of constellations drawn per sky
region. Our results show distinct types of line figures, and that many folk
astronomies with oral traditions have widespread similarities in constellation
design, which do not align with cultural ancestry. In a minority of sky
regions, certain line designs appear universal, but this is not the norm: in
the majority of sky regions, the line geometries are diverse.
