Delta IV, also called Delta or Dhei, was the fourth planet of the Delta Triciatu system (TOS novel: The Fearful Summons) in the Alpha or the Beta Quadrant. (ST reference: Star Charts) Delta IV was homeworld of the Deltan species. (TOS movie: The Motion Picture)
It was governed by the Deltan Union, which joined the United Federation of Planets in 2223. (ST reference: Star Charts) In the late 23rd century, Delta IV was a full-status Federation member. (FASA RPG module: The Federation) It had no particular capital city. (ST reference: Star Charts)
As of reference stardate 2/2306.1 (c. 2287), the planet had a population of 8.52 billion people, including 6 billion Deltans. (FASA RPG module: The Federation) In the 2370s, the planet had a population of 3.8 billion. (ST reference: Star Charts)
- This sharp decrease in population, by over 50%, over the century may be attributed to the Borg/Cyberman attack of 2368, which saw at least half of the planet overrun.
As Deltans preferred to live close together, their planet was famous for its many cities and cosmopolitan personality. The cities were gleaming, with tall spires and domes, and dense with meeting places, such as restaurants, music clubs, shopping centers, debating halls, and so on, for people to meet and talk. (Decipher RPG module: Aliens)
The planet and its people focused primarily on cultural matters. The planet had a technological/sociopolitical index of 988767-87 and a planetary trade profile of ABABCCB/B(B). (FASA RPG module: The Federation)
One of the closest inhabited planets to Delta IV was Carrea. The Carreon and the Deltans had been rivals since first contact, sometime prior to the late 22nd century. (Star Trek: Gateways novel: Doors Into Chaos; ST novel: Articles of the Federation)
Prior to contact with the Federation, Delta IV was already a famously cosmopolitan world. The first contacts were with Andorians, while later contacts with humans were described as "quirky", as neither side knew what to expect of the other. (Decipher RPG module: Aliens) Not long after the Deltans developed space-flight, the USS Austin discovered Delta, and soon learned of the power that Deltan pheromones had on humans. After this lead to the death of an officer from the Austin, the Federation placed a quarantine around Deltan space, forbidding all vessels from entering until a solution to the problem of pheromones could be found. The Deltans agreed to refrain from intimacy with humans. (FASA RPG module: Star Trek IV Sourcebook Update)
On stardate 45635.2, 2368, Delta IV was the target of a joint Borg–Cyberman surprise attack. The largest cities were targeted, followed by the destruction of command and control infrastructure. The USS Potemkin and USS Lassiter fought the Borg cube though with no success. At least half of the planet was overwhelmed in a matter of minutes, forcing its prime minister to order a planetary evacuation well before Starfleet's defensive task force could arrive. (TNG - Assimilation² comic: "Issue 1") The USS Enterprise-D responded to a distress call and arrived in the Delta system, but was immediately fired upon. It fled and the Borg–Cyberman fleet gave chase. (TNG - Assimilation² comic: "Issue 2")
Delta IV was attacked by Dominion forces during the Dominion War, resulting in the contamination of their water table. This resulted, by 2379, in the breakdown of their water reclamation system. Delta attempted to obtain a new Carreon-designed system, and after four months of negotiation, agreed to allow a Carreon scientific base on planet Brannik IV in exchange for this new system. (ST novel: Articles of the Federation)
Delta IV was a Class M world. (FASA RPG module: The Federation; ST reference: Star Charts) It had a cool temperate climate, a thin atmosphere and a 20-hour day. (FASA RPG module: The Federation) The sky was a soft blue thanks to its parent star. (FASA RPG module: Star Trek IV Sourcebook Update).
The planet was characterized by turbulent tropical oceans, small continents and island chains. These were usually covered with lush forests and jungles, with deep valleys and jagged mountains. Large swathes of the planet remained undeveloped, so much of it appeared wild and untamed, offering a number of natural attractions. (Decipher RPG module: Aliens)
It had a total surface area of 625,000,000 square kilometers and, with 60% land mass, a total land area of 375,000,000 square kilometers. About 55% of its makeup was normal metals, 15% was radioactive elements, 10% was gemstones, and it had only trace amounts of special minerals and industrial crystals. (FASA RPG module: The Federation)
While the ST reference: Star Charts shows the Deltan homeworld in the Alpha Quadrant, the Decipher RPG module: Starfleet Operations Manual states that this is a Beta Quadrant planet. For the purposes of this wiki, this is categorized as being from one of the quadrants without specification as to which.