Which Hellenistic queen's Berenice's Hair became a constellation?

Berenice II of Egypt, who around 245 BC vowed her hair to a temple if her husband returned safely from war in Syria. He did; she cut it off and dedicated it; and the next morning it had gone from the temple.

The court astronomer Conon produced the diplomatic solution: the gods had been so pleased that they had placed it in the sky, as a faint scatter of stars near Leo's tail. It is the only constellation named for a real historical person, and one of the very few whose date and circumstances of invention are known. Callimachus wrote a poem about it, later reworked by Catullus, in which the lock itself speaks and complains about being separated from her head.

The patch turned out to be significant. Those faint stars are not a cluster but our view out through the least obstructed direction from the galaxy's disc, which is why the region is thick with distant galaxies - the Coma Cluster sits there. It was in that cluster that Fritz Zwicky, in 1933, found the galaxies moving far too fast for their visible mass to hold them together, and proposed dark matter. Berenice's own end was less decorative: she was murdered on her son's orders in 221 BC.