Star Trek Fact Or Fiction: Vulcan

Astronomers announced the discovery of an exoplanet with 8.47 times Earth's mass and twice Earth's radius in the 40 Eridani star system, distant 17 light-years from our Sun. In the Star Trek universe, the Eridani constellation is mentioned as the star system where the planet Vulcan is located, homeworld of Commander Spock.

The USS Enterprise in orbit of Vulcan, from Star Trek: The Original Series - Remastered.

In Star Tek – The Original Series the location of Vulcan was never identified. Vulcan is mentioned as planet various times in the first season, but only in the pilot of the second season, “Amok Time” aired September 15, 1967, it is visited by Commander Spock, Captain Kirk and chief medical officer McCoy. Vulcan is described as an Earth-sized world, mostly covered by deserts and mountains, with a red sky glowing above a barren landscape. 

As it orbits its sun on a very narrow orbit, surface temperatures are higher as on Earth. Also, the atmosphere is very thin, barely breathable, and non-Vulcans have a hard time adapting to the harsh environment. According to Star Trek lore, the desert-planet Vulcan orbits its sun together with the planet T´Khut, a geologically very active lava-planet.

In the movie Star Trek 2, released in 1982, the star 40 Eridani A is mentioned as Vulcan's sun. In 1991 Gene Roddenberry, creator of Star Trek, published a short article together with astrophysicists Baliunas, Donahue and Nassiopoulos, arguing that the constellation of Eridani would be the most fitting place for Vulcan. The real 40 Eridani system is a triple star system, with Eridani A as primary star accompanied by a red and a white dwarf star, named respectively Eridani B and Eridiani C. Only Eridani A is shining stable enough to host a hypothetical habitable planet. Eridani B emits too much dangerous radiation and Eridani C is prone to flares, sudden eruptions of energy and matter emitting lethal doses of X-rays. As Eridani A is smaller than our Sun, also the habitable zone, where a planet could exist with liquid water, is narrower. Unlike the fictional planet Vulcan, the real exoplanet seems to be a Super-Earth or a small gas giant. According to the published preliminary results the planet orbits its star in just 39 to 40 Earth days, along the inner limit of the habitable zone.