Denea is a swampy Class M planet located within the Uncharted Territories, just outside of Peacekeeper Space. It is orbited by two natural satellites. As of the end of the Earth's 20th century, the Deneans were aware of the existence of other species within the Milky Way but had not yet encountered them.
The planet, however, was rich in clorium (or "onlux" as the Deneans call it) -- a useful agent for numbing Leviathans. Deneans made semi-official first contact with extraterrestrials when Moya and her crew hid on the planet in order to stop the paddac beacon attached to Moya's neural nexus from broadcasting its signal. Although the event was never made public, Lyneea and Fostro worked to prepare their people for future alien contact.
In truth, there were clear indications that aliens had visited the planet some time in its ancient past -- this could be determined by the presence of translator microbes in the planet's soil and atmosphere.
Denea appeared in Farscape's first season.