Bela Tegeuse

Bela Tegeuse Fifth planet in the Kuentsing system. Third stopping point for the Zensunni migration. Hiding place for ruler of Ix after the Tleilaxu? conquered Ix.

Oxygen-nitrogen atmosphere, and low photosynthesis levels. It's photosynthesis level was partly due to the dimness of both its stars (a red secondary and a white dwarf primary), and partly because of its constant thick cloud cover locking the weather cycle into an unbreakable pattern of rain and gloom.

Sources: The Machine Crusade?, House Atreides?, Paul of Dune?, Chapterhouse: Dune?

On the net: Dune Wikia,
Related: Betelgeuse,

Sources: House Atreides, Paul of Dune?