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A light year (abbreviated ly) was a unit of measurement used for establishing distance from one location to another in space. One light year described the distance light traveled in a vacuum in one Earth year. The length of this unit was standardized by the UFP Standards Measurement Bureau. Other spacefaring species, such as the Sheliak, had their own unit of distance. (TOS: "Where No Man Has Gone Before"; TNG: "The Ensigns of Command")


Located less than twenty light years from the Sol system, Terra Nova became the first extra-solar colony of Earth in 2078. (ENT: "Terra Nova")

The planet housing the Vulcan monastery at P'Jem was, according to the Vulcan star charts, just a few light years off of the current heading of Enterprise NX-01. (ENT: "The Andorian Incident")

In May 2151, Enterprise found the Triglobulin harvester's starship almost three light years away from the nearest star system. (ENT: "Fight or Flight")

In February 2152, Captain Jonathan Archer told Keyla that Risa was located ninety light years from Sol and was the furthest any of his people had gone at that point. (ENT: "Two Days and Two Nights")

In September 2152, Enterprise was in orbit of an uninhabited planet. At this time the ship was over one hundred light years away from Earth and more than twenty light years away from the Takret homeworld. It encountered a neutronic wave front which spanned more than half a dozen light years. (ENT: "The Catwalk")

Later that year, Enterprise discovered what was determined to be a 31st century Earth vessel. At that point, Enterprise was a hundred light years from Earth and more than thirty light years from the nearest trade route with no other ships or ships or inhabited star systems for several light years, making the matter of the initially unidentified craft and its Human pilot a mystery. (ENT: "Future Tense")

When the computer identified the numerical sequence sent by the Borg into the Delta Quadrant in 2153, it became pulsar frequencies with geometric light year measurements. (ENT: "Regeneration")

In the Treaty of Armens (2255), it was stipulated, "Third party assistance may be requested from a Federation Starfleet vessel or a Sheliak Corporate spacecraft if the distance from the vessel to the respective homeworld is greater than five thousand (5.0e3×103) light years. UFP Standards Measurement Bureau Units. Assistance may also be requested if the vessel is less than 1,000 light years from a standard UFP subspace relay booster station." (TNG: "The Ensigns of Command")

Eagle-12, containing a Federation space station, and Gamma Hydra, home to an Andorian colony, were respectively located three and six light years away from a binary star system at the edge of Federation space. As such, they were considered vulnerable to Klingon attack should the USS Shenzhou fail to find a diplomatic solution to the standoff with the Sarcophagus prior to the Battle of the Binary Stars. (DIS: "The Vulcan Hello")

In 2256, the USS Glenn, using an experimental spore drive, managed to travel back and forth into the Beta Quadrant, a ninety light year jump, in 1.3 seconds. (DIS: "Context Is for Kings")

In 2293, the USS Enterprise-B, having just left Spacedock One, was three light years away from the transport ships SS Robert Fox and SS Lakul when they were caught up in the Nexus, making the Enterprise the closest Starfleet ship to mount a rescue. (Star Trek Generations)

In 2364, the USS Enterprise-D was hurled 2,700,000 light years, through two galaxies, to the Triangulum Galaxy by the Traveler during warp field tests. In an attempt to return to their last position, the Enterprise was again brought forward over a billion light years to the end of the universe, the furthest point reached by a Starfleet vessel. Ultimately, however, the Traveler was able to reverse the course and return Enterprise back to where it started. (TNG: "Where No One Has Gone Before")

In 2365, Q propelled the Enterprise seven thousand light years to System J-25 and back again following their first contact with the Borg. (TNG: "Q Who")

When Commander Benjamin Sisko welcomed the first guest from the Gamma Quadrant in the Alpha Quadrant, a Tosk, he told him that he traveled almost ninety thousand light years through the wormhole. (DS9: "Captive Pursuit")

In 2369, a Vanoben transport was raided two light years away from Deep Space 9. (DS9: "Vortex")

The same year, Sisko told Kai Opaka that the Gamma Quadrant was seventy thousand light years away from Bajor. (DS9: "Battle Lines")

The Caretaker's array was capable of generating a displacement wave capable of dragging ships many light years across the Milky Way Galaxy, doing so in 2371 when it swept the Maquis ship Val Jean and the USS Voyager over seventy thousand light years from the Badlands to its position in the Delta Quadrant. (VOY: "Caretaker")

Quark recalled that he was serving on a Ferengi freighter hundreds of light years from Ferenginar when the Great Monetary Collapse hit. (DS9: "Homefront")

In 2373, the USS Defiant was transporting the Orb of Time back to Bajor when Arne Darvin used it to transport the Defiant back in time to the year 2268 over two hundred light years from their last position, where they found the USS Enterprise in orbit of Deep Space Station K-7. (DS9: "Trials and Tribble-ations")

Traveling from 2373 to 2063, Captain Jean-Luc Picard characterized the United Federation of Planets to Lily Sloane as consisting of over one-hundred fifty member worlds spread across eight thousand light years. (Star Trek: First Contact)

In 2374, as her final gift to the Voyager crew, Kes propelled the ship over nine thousand five hundred light years closer to Earth, eliminating ten years off the crew's journey. (VOY: "The Gift")

Later that year, Voyager discovered an ancient relay network spanning across the galaxy, which they used to locate and contact the USS Prometheus, a Starfleet vessel on the edge of the Alpha Quadrant over sixty thousand light years away. (VOY: "Message in a Bottle")

The Hirogen pursued a member of Species 8472 across fifty light years. A group of Hirogen ships pursued the prey to Voyager's position; with the nearest ship half a light year away, Chakotay predicted that Voyager would be intercepted within four hours maximum. (VOY: "Prey")

Voyager spent a month crossing a nebula which spanned one hundred ten light years. (VOY: "One")

At the end of that year, Voyager used a quantum slipstream drive to travel three hundred light years before it collapsed. Several months later, the crew revisited this technology and were able to travel another ten thousand light years before the slipstream dispersed. The technology was deemed too dangerous for use after this occurrence and was dismantled. (VOY: "Hope and Fear", "Timeless")

"The Void" was a region in the Delta Quadrant where no star systems existed within a distance of two thousand five hundred light years which could be passed in an instant via a spatial vortex, which was used by Voyager in early 2375. (VOY: "Night")

In 2378, Voyager Captain Kathryn Janeway credited the feat of making more first contacts than any other Federation starship since the era of James T. Kirk and the original USS Enterprise to being "the only Federation starship within thirty thousand light years." (VOY: "Friendship One")

Later that year, Sphere 634, containing Voyager, passed through a transwarp conduit and arrived less than a light year from Earth. (VOY: "Endgame")

In the 26th century of a possible future presented to Jonathan Archer by temporal agent Daniels, the Battle of Procyon V was fought amid a trans-dimensional disturbance created by the Sphere-Builders that extended fifty thousand light years in all directions and growing. (ENT: "Azati Prime")


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Background information[]

A light year is the distance that light travels in one Earth year. It is approximately equal to 9.46e12×1012 kilometers, or 5.88e12×1012 miles. The exact length of a light year depends on the length used for one "Earth year". The IAU uses a Julian year of 365.25 days, while other sources may use a Gregorian year of 365.2425 days, or another year altogether.

According to Michael Okuda, the location between Earth and Vulcan, sixteen light years, is ninety-three trillion miles. ("The Andorian Incident", text commentary, ENT Season 1 DVD special feature)

Source year (days) light year (kilometers) light year (miles)
IAU 365.25 9,460,730,472,581 5,878,625,373,184
Gregorian 365.2425 9,460,536,207,068 5,878,504,662,190

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