Petersen Graph

The Petersen graph is an undirected graph with ten vertices and fifteen edges, most commonly drawn as an outer pentagon and an inner pentagram connected by five spokes. Julius Petersen constructed it in 1898 as the smallest bridgeless cubic graph that cannot be properly edge-colored with only three colors, disproving a conjectured generalization of an earlier result by Alfred Kempe. Because it combines high symmetry with a habit of failing plausible-sounding conjectures, the Petersen graph has become one of the standard counterexamples in graph theory, described by Donald Knuth as a configuration that serves as a counterexample to many optimistic predictions about what might be true for graphs in general. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/