From Halopedia, the Halo wiki
Ixion is a minor planet in the Sol system. It had been colonised by humanity by the 26th century, and fell under the jurisdiction of the Unified Earth Government. Darren Leone, acting captain of the UNSC Dark Was the Night as of some time in 2553, was born on the colony.
The minor planet was first discovered in 2001, and was christened "Ixion" in 2002, after the Greek figure Ixion, a king who was punished by Zeus and bound eternally on a wheel of fire in the underworld.