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This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.

Trill was an inhabited class M planet in the Trill system of the Alpha Quadrant. It had a single moon. This was the homeworld of two sentient species who shared a symbiotic relationship: the Trill, a warp-capable humanoid species, and the non-humanoid Trill symbionts. The planet was governed by the Trillian government, which enforced Trill law. Mak'ala was the capital city. (DS9: "Invasive Procedures", "Equilibrium"; DIS: "Forget Me Not")

Astronomical data[]

Trill planetary data

Planetary data for Trill

Trill orbited its sun at a distance of 1.215 AU, with an orbital period of 483 solar days and a Keplerian ratio of 0.967. Its rotation period was 26.6 hours long. The planet had a radius of 6,493 kilometers and a surface area of five hundred million square kilometers. The estimated age of the planet was 4.682 billion years. Its mass was estimated to be 5.872e24×1024 kilograms, giving it a surface gravity of 0.98 g.

The atmosphere of Trill was composed of 76% molecular nitrogen, 21% molecular oxygen, 0.8% argon, 0.5% water vapor, and 0.3% carbon dioxide, with trace amounts of methane. The surface had an atmospheric pressure of 1.012 bar and a mean temperature of 297 Kelvin. (DIS: "Jinaal")


Trill surface, 3189

Forest near the Caves of Mak'ala (3189)

Natural features on Trill included forests, lakes, canyons, and caves. Trill's oceans had a purple tint when viewed from space. (DS9: "Past Tense, Part I", "Equilibrium"; DIS: "Forget Me Not", "Jinaal")

Lifeforms native to Trill included the itronok and the ina raptor, as well as birds and flying fish (DIS: "Forget Me Not", "Jinaal")

Geographical features[]

Points of interest[]


Trill planet

Trill in 2371

The symbionts' ancestral home was in the underground caves, including the Caves of Mak'ala. The Trill had information on joinings as far back as the 12th century. (DIS: "Forget Me Not")

In 2367, the USS Enterprise-D had to contact the Trill homeworld to send a replacement host for an injured ambassador, Odan. (TNG: "The Host")

In 2371, the USS Defiant traveled to Trill when Jadzia Dax's life was endangered by suppressed memories of her previous host, Joran Belar. (DS9: "Equilibrium")

In 2375, the USS Destiny was en route to Trill with the Dax symbiont, which had been injured, when the symbiont took a turn for the worse. As a result, it had to be joined with Ezri Tigan, the only Trill on the Destiny. (DS9: "Shadows and Symbols")

Jack Crusher, under his alias "John Carson", was charged with disorderly intoxication on Trill in the late 24th century. (PIC: "Disengage")

Trill advertisement

Advertisement for a beach on Trill

In 2402, Deanna Troi and William T. Riker considered taking a beach vacation on Trill. (PIC: "The Last Generation")

In 3069, The Burn decimated the Trill population, resulting in the planet becoming more insular in an attempt to stave off extinction. Despite this, a century later there were still not enough viable hosts for the remaining symbionts. Trill was among the Federation members that chose to secede during this period.

It is unclear when Trill first became a member of the Federation; its status in the 24th century is ambiguous.

In 3189, the time-displaced USS Discovery traveled to Trill to help Adira Tal access the Tal symbiont's memories. (DIS: "Forget Me Not") After the defeat of Emerald Chain, Trill rejoined the United Federation of Planets. (DIS: "That Hope Is You, Part 2")




Background information[]

In the series bible for Star Trek: Deep Space Nine, it was said that the underground of Trill and the planet's surface were where the Trill symbionts and humanoids lived, respectively. It was also stated that "an environmental disaster" led the two species to begin integrating with each other. [1]

As there were two make-up configurations designed for the Trill, Jadzia Dax actress Terry Farrell once suggested that "the north of Trill" was the birthplace of the simpler-looking Trill whereas the planet's south was where the more elaborate physical design, involving spots, originated. (Cinefantastique, Vol. 23, No. 6, p. 21) While filming DS9 Season 1 finale "In the Hands of the Prophets", Farrell also expressed hopes of seeing Trill in the second season of Star Trek: Deep Space Nine, saying, "I'd like to go to the planet where I'm from." (Cinefantastique, Vol. 24, Nos. 3/4, p. 98.)

The name of the Trill homeworld was first established as "Trill" in the second season outing "Invasive Procedures". The planet makes its first appearance in the third season episode "Equilibrium". Portraying the planet in that episode proved highly expensive. Some of the Trill exteriors shown in "Equilibrium" were filmed on location in Huntington Gardens. "I think there were a lot of interesting things about the Trill homeworld that you found out in the episode," commented René Echevarria, who wrote "Equilibrium"'s script. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, pp. 84 & 85.)

For the Star Trek: Discovery episode "Forget Me Not", the exterior shots for Trill were filmed at the Royal Botanical Gardens rock garden in Hamilton, Ontario, Canada. The building, a visitor center for the garden, was designed by CS&P Architects. [2]

Star Trek: Star Charts (p. 33) and the Star Trek Encyclopedia, 4th ed., vol. 2, p. 421 identified the Trill homeworld as Trillius Prime and that it was governed by the Trill Symbiosis, admitted into the Federation in 2285. As of 2370, the planet was populated by 650 million Trill and 11 million symbionts, though the existence of symbionts was not widely known prior to 2367.


Worlds of Star Trek Deep Space Nine 2

Worlds of Star Trek: Deep Space Nine, Volume Two focuses on Trill and Bajor.

The Star Trek: Federation Travel Guide calls out local attractions including the Teneran Ice Cliffs (3/3 stars) in the southern hemisphere and the caves of Mak'ala (2/3 stars.) "The Interplanetary Bar and Grill" serving foods from hundreds of worlds is highlighted, noting "local cuisine failed to tempt our reviewers palate." The Selipsis is identified as Trill's largest and oldest beach resort. "Grow old in wisdom" is noted as a local key phrase to know.

Trill is depicted in several of the short stories in the novel anthology The Lives of Dax, the novel Revenant and the novella Unjoined.

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