The alternate reality was the new reality created by a temporal incursion of the Narada from the year 2387. Accidentally traveling back to the year 2233, Nero, the captain of the Narada, destroyed the USS Kelvin, killing George Kirk and Richard Robau. Spock arrived in the alternate reality in 2258 and was captured by Nero, who used red matter to destroy Vulcan. However, Nero's attacks united the crew of this reality's USS Enterprise years earlier, to foil his attempt to destroy Earth. (Star Trek)
In the prime universe, the supernova of 2387 threatened the entire galaxy. Ambassador Spock was able to halt the supernova, via the use of red matter to create an artificial singularity, or black hole, which absorbed the exploding star, but was too late to save the planet Romulus from destruction. The Narada, a Romulan mining ship under the command of Captain Nero, was pulled into the black hole, followed by Spock's ship, the Jellyfish.
Nero placed blame on the Federation for the loss of his homeworld and sought revenge. He emerged from the black hole in 2233. The USS Kelvin was the first ship that Nero encountered and attacked; Captain Richard Robau promoted his first officer, Lieutenant Commander George Kirk, to captaincy before ordering the evacuation of the ship and agreeing to come aboard the Narada. There, Captain Robau was interrogated regarding the whereabouts of Spock, with whom Robau was unfamiliar and, moments after he informed Nero of the current stardate, he was murdered.
Nero then proceeded to attack the Kelvin. Kirk used the Kelvin's weapons to prevent Nero from destroying the evacuating shuttles departing the ship, ultimately sacrificing himself by ramming the Kelvin into the Narada. Kirk's actions saved some 800 lives, including his wife, Winona Kirk, and their newborn son, James, but failed to destroy the Narada.
As a major consequence of these events, James Kirk grew up without his father and without the ambitions his father gave him in the prime reality. However, he was persuaded by Christopher Pike to join Starfleet, five years later than he had done in the prime reality.
In the meantime, other events happened differently. Pavel Chekov was born in 2241, while the Romulans were confirmed as relations of the Vulcans. Plans for the Constitution class were pushed back by a decade and the USS Enterprise began construction in 2255 at the Riverside Shipyard in Iowa. It was launched three years later, as the Federation flagship. Spock was already promoted to Commander by this point. Starfleet continued using the simple <earth calendar year>.<day of the year> format for stardates, and began using gold, blue and red colors for their uniforms. They also adopted the Kelvin assignment patch as the sole Starfleet insignia. The Vulcan High Command was reinstated as the Vulcan High Council.
Destruction of Vulcan
In 2258, Nero captured the Jellyfish as it emerged from travel through the black hole. He marooned Spock on Delta Vega, and despite the efforts of the USS Enterprise, he used a portion of the remaining red matter aboard to destroy the planet Vulcan and six billion of its inhabitants, including Amanda Grayson. While marooned on Delta Vega, Spock encountered the alternate James T. Kirk and made him aware of the prime reality and the altered past. He also met Montgomery Scott and gave him the formula for transwarp beaming, which Scott used to transport Kirk and the young Spock to the Narada, allowing them to prevent a similar fate for Earth by detonating the Jellyfish and its red matter to destroy the Narada.
Afterward, Christopher Pike was promoted to Admiral and Kirk and Spock became captain and first officer of the Enterprise, which was officially launched on a voyage of exploration, with much of its commanding crew comprised of those who served aboard it in the prime reality during 2267: Kirk, Spock, Scott, Chekov, Leonard McCoy, Hikaru Sulu and Nyota Uhura. Spock began a relationship with Uhura following a reconciliation with his father, Sarek, and the deaths of his Human mother as well as most of his own people. Ambassador Spock intended to found a new Vulcan colony for the 10,000 Vulcan survivors. (Star Trek)
Starships and space stations
- USS Antares
- USS Armstrong
- USS Enterprise
- USS Farragut
- USS Hood
- USS Kelvin*
- Klingon warbird*
- USS Mayflower
- USS Newton
- Regula I
- Shuttle 12091
- Shuttle 78072
- Starbase 1
- USS Truman
- USS Wolcott
* denotes a ship predating the creation of the alternate reality.
** denotes a ship imported from the prime reality.
The alternate reality runs parallel to the prime reality as a new quantum reality. The prime reality is where many of the events seen in the Star Trek universe have occurred and, according to Star Trek writers Alex Kurtzman and Roberto Orci, their film allows the prime reality to continue.
This intent is also evident in the script of Star Trek.  While not completely audible in the film, before being teased by his classmates, young Spock is asked by the computer in the learning center on Vulcan: "What is the central assumption of Quantum Cosmology?" To which Spock replies: "Everything that can happen does happen in equal and parallel universes."
As the alternate reality is merely divergent rather than a completely new universe, this means backstory elements pertaining to anything before 2233 hold true for both timelines. Director J.J. Abrams said here that "It's actually nice when you're given a box.... when you're given parameters that you have to honor because it gives you limits and then you know that within those boundaries you can be creatively risky."
Star Trek screenwriter Roberto Orci (in a post on Ain't It Cool News  as well as in an interview with Star Trek Magazine ) and J.J. Abrams (in an interview with MTV, conducted between the two aforementioned statements from Orci ) established a reason why technology in the alternate reality appears to be more advanced than it is during the same period in the prime reality; scans of the 24th century Narada, taken by the Kelvin, were brought back to Starfleet by the survivors on the Kelvin's shuttles.
The Star Trek screenplay contains a musing from Spock Prime, having told by Kirk that Chekov, Sulu, and Uhura were all serving in the Enterprise (by this point he takes it for granted that McCoy is as well), while Scotty is on the same planet as the two of them, that Kirk's implausible meetings with the people who would become his crew in the prime reality may be the result of the timeline trying to repair itself from Nero's damage. The film's novelization by Alan Dean Foster preserves this exchange.
Writers Mike Johnson and Tim Jones wrote Star Trek: Countdown, a comic book prequel to Star Trek expanding on the events in the prime reality leading to the Narada's arrival back in time. Johnson and Jones subsequently collaborated on Star Trek: Nero, based on the deleted scenes regarding Nero's imprisonment, and Star Trek - The Official Motion Picture Adaptation. Johnson writes the ongoing Star Trek comic, launched in September 2011, which explores how some classic stories unfold in the new timeline.
Four novels set after Star Trek were set to be published in 2010: Refugees, Seek a Newer World, More Beautiful Than Death and The Hazard of Concealing. The novels were announced as being on hold as of 14 January 2010. On his blog, Refugees author Alan Dean Foster speculated the hold was due to the plots of the novels possibly conflicting with the next film. Two years later, Christopher L. Bennett posted "All I can say is that most of the speculations I hear about why the books were pulled are wrong. It wasn't about conflicts with the second movie." A series of young adult books, Star Trek: Starfleet Academy, following the characters during their time at the Academy, began in November 2010.
In The Needs of the Many, a novel based upon the Star Trek Online series, when Dulmur, one of the Department of Temporal Investigations agents from DS9: "Trials and Tribble-ations", is institutionalized and suffering from temporal psychosis, he has memories of not only his timeline, but of several others as well - including one where Vulcan was destroyed a century prior. Another novel Watching the Clock goes into detail about how and why some forms of time travel create parallel alternate realities and others lead to the overwriting of the same timeline. Bennett, the author, stated this was an in-universe explanation for the co-existence of the prime and alternate realities.