Vulcan (hypothetical planet) Vulcan (hypothetical planet) Vulcan is a small hypothetical planet that was proposed to exist in an orbit between Mercury and the Sun. Attempting to explain peculiarities of Mercury's orbit, the 19th-century French mathematician Urbain Le Verrier hypothesized that they were the result of another planet, which he named "Vulcan". A number of reputable investigators became involved in the search for Vulcan, and despite occasional claimed observations, no such planet was ever confirmed. Peculiarities in Mercury's orbit have now been explained by Albert Einstein's theory of general relativity. Searches of data gathered by NASA's two "STEREO" spacecraft have failed to find
Planet V Sun after entering the ν secular resonance. As an initial test of the Planet V hypothesis, Chambers and Lissauer conducted 36 computer simulations of the Solar System with an additional terrestrial planet. A variety of parameters were used to determine the impacts of Planet V's initial orbit and mass. The mean time at which Planet V was lost was found to increase from 100 Myr to 400 Myr as its initial semi-major axis was increased from 1.8 to 1.9 AU. Results consistent with the current Solar System were most common with a 0.25 Mars mass Planet V. In cases with