I wonder why Juno and not Hygiea...
Ceres, Vesta, and Pallas are 3 of the 4 largest asteroids, with Hygiea being the 4th, however Juno is ranked as number 11.
The only thing I can guess is because Juno was a much bigger Goddess than Hygiea. Juno was Queen of the Gods, whereas Hygiea was only a minor Goddess of healing and medicine.