Meridian
Meridian was the first and only planet in the Gamma Quadrant's Trialus system.

Millenia ago, the planet became the new home of members of an expedition that stranded there. They established a settlment in the southern hemisphere. By 2371, there were thirty inhabitants living in the settlement, with more having lived here in the past; however, as a result of the time being available for reproduction growing shorter, the population had declined.

The core of Trialus periodically built to a cascade effect at the quantum level, causing Meridian to shift from one dimension to another. The planet appeared in regular space every sixty years. When in the other dimension the planet's inhabitants existed as pure consciousness and the planet and everything on it disappeared from normal space. This had been the case for a thousand years prior to 2371. 

By 2371, however, the planet had been undergoing changes for several centuries and its time in normal space had been growing shorter with each visit. At that time, Meridian would manifest in normal space for only twelve days, and it was predicted that within a few centuries their stay would last only minutes. When that happened, the planet would become unstable, being unable to exist in either dimension, and, as a result, both the planet and everything on it would cease to exist.

That year, the , on a mission of exploration in the Gamma Quadrant, was present when Meridian returned to normal space for the first time since 2311. The crew of the starship studied Trailus along with the scientists of Meridian and discovered an instability that was causing the shortened stay of the planet in normal space. With the help of the Defiant, the inhabitants were able to stabilize the star and expected their next manifestation to last thirty years, long enough to begin having families again. Jadzia Dax attempted to remain on Meridian as it shifted realities, but was unable to as her presence would have destroyed the planet. ()

Inhabitants

Appendices

Background information 
According to StarTrek.com, this planet's technical name was Trialus I.  The  classified Meridian as a class M planet. Furthermore, in the note section of the entry, it is noted that "the painted forest backdrop used outside the Meridian hall was rented from , which had originally created the backdrop for the movie . The Meridian hall itself was also seen (in modified form) as the Klingon Great Hall in  (DS9), the Albino's lair in  (DS9), and Masaka's temple in  (TNG)."

External link 
 

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Planets
Colonies