The Delos system was an inhabited planetary system consisting of a primary and at least four planets, including Ornara and Brekka.
Before 2164, a Federation scout made contact with this system. The ship disovered two inhabitable planets; one of which was on the verge of acquiring space travel. Two centuries later in 2364, the starship USS Enterprise-D visited the system to chart the solar flare activity of the star Delos. (TNG: "Symbiosis")
According to StarTrek.com, there were two systems named Delos. [1]
"DELL-ose" was the pronunciation for this planet's name from the script pronunciation guide. [2]
