40 Eridani A

40 Eridani A was the primary of the 40 Eridani system. This system was located in the Sector 001 (or Sol sector), which was a region of space in the Alpha Quadrant.

The system orbiting this star was home to the Federation's 40 Eridani A Starfleet Construction Yards, building place of the starships Brattain and Phoenix. ( dedication plaques)

Appearances

 * USS Phoenix's dedication plaque made for
 * USS Brattain's dedication plaque made for

Background information
It has never been canonically established that 40 Eridani A was the location of Vulcan, but it has been a popular piece of information throughout licensed works and fandom. The reference has worked its way into a number of background graphics and artwork, for example, the dedication plaques listing the fleet construction shipyards there. References to this star system as Vulcan's date back to James Blish's adaptation of in the book Star Trek 2, as well as a mention in the Star Fleet Technical Manual by Franz Joseph. On-screen statements of Vulcan being 16 light years away from Earth in and  also support 40 Eridani A as the location of Vulcan.

In 1991, Star Trek creator Gene Roddenberry, along with three scientists from the Harvard - Smithsonian Center for Astrophysics, endorsed 40 Eridani A as Vulcan's sun (rather than Epsilon Eridani, which is occasionally misidentified as Vulcan's sun) stating, in part: "We prefer the identification of 40 Eridani as Vulcan's sun because of what we have learned about both stars at Mount Wilson ... based on the history of life on Earth, life on any planet around Epsilon Eridani would not have had time to evolve beyond the level of bacteria. On the other hand, an intelligent civilization could have evolved over the aeons on a planet circling 40 Eridani. So the latter is the more likely Vulcan sun." 

The Star Fleet Medical Reference Manual also referenced the Vulcan species as "Homo Eridani."

Star Trek: Star Charts
According to the Star Trek: Star Charts, the 40 Eridani (Omicron 2 Ceti) system was located in the Vulcan Sector (Sector 005), Beta Quadrant. This was a trinary star system. The orbital period for this system was 248 years. Two thousand years ago, 40 Eridani A was a destination on the Debrune trade routes. On his final voyage, in 2120, Zefram Cochrane visited this system. In the mid-22nd century, 40 Eridani A was a destination on the Earth trade routes. (Pages 19, 36, 45, 58, & 60)
 * 40 Eridani A: This star was classified as a K1V star with an of 6.0. This system had three planets, one of which was inhabitable, and an asteroid belt.
 * 40 Eridani B: The secondary star was classified as a AVII star with an absolute magnitude of 11.2. The distance between Eridana A and Eridani B was 400 astronomical units.
 * 40 Eridani C: The tertiary star was classified as a M4V star with an absolute magnitude of 12.3. Both Eridani B and C had no planets. The distance between Eridana B and C was 44 astronomical units.