An astronomical unit (abbreviated au) was a unit of length on the interplanetary scale, roughly equal to the (average) distance between Earth and Sol. One astronomical unit was equal to 150 million kilometers, or approximately 93 million miles.
Comparative list of length
- The location of Klingon prison ship Captain Gabriel Lorca was being held aboard was located 0.7 au from USS Discovery at the time of its discovery. (DIS: "Choose Your Pain")
- When Captain Sisko's runabout was approached by two Jem'Hadar attack ships in the Badlands in 2373, they initially were 1 au away. (DS9: "Blaze of Glory")
- The intense energy cloud created by V'ger was approximately 2 au in diameter. (Star Trek: The Motion Picture)
In the original version of the film, V'ger's cloud was actually 82 au across. At their farthest point from each other (the aphelion), Earth and Pluto are just over 49 au apart. This would have made V'Ger's cloud almost twice that length, engulfing over half the solar system. As a result, the cloud size was toned down to a more reasonable number in the 2001 director's edition but even then, 2 au, the diameter of the Earth's orbit, is still an enormous size.
- The map of the inner system of the Talos system depicted the distance from the binary stars on a line. At every ten intervals, there was a mark which represented one astronomical unit. The map showed that the inner system reached 3.4 au. (TOS: "The Cage")
- The nucleogenic cloud being measured 7 au in diameter. (VOY: "The Cloud")
- When searching for Harry Kim in 2371, the USS Voyager performed a subspace scan with a scan radius of 10 au. (VOY: "Emanations")
- Starbase 1 was located 100 au from Earth. (DIS: "The War Without, The War Within")
- The USS Europa was still 800 au behind the rest of the fleet that had already arrived at the location where the later Battle of the Binary Stars occurred. (DIS: "Battle at the Binary Stars")