 The planet was proposed as a hypothesis in 1859, and abandoned not later than 1915.The name "Vulcan" has been used for various other fictional planets, in and out of the Solar System, that do not correspond to the hypothetical planet Vulcan.The planet Vulcan in the "Star Trek" franchise, for instance, is specified as orbiting 40 Eridani A.

Counter-Earth was a hypothetical planet sharing an orbit with Earth, but on the opposite side of the Sun (hence Earth and Counter-Earth would always be invisible to each other).