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 Nine distant orbits around another star, or rogue planet, leaving one in a stable orbit around the Sun via a process similar to the capture of irregular satellites around the giant planets. If the planet originated in a system with a number of Neptune-massed planets, and without Jupiter-massed planets, it could be scattered into a more long-lasting distant eccentric orbit, increasing its chances of capture. Although the odds of the Sun capturing another planet from another star can be higher, a wider variety of orbits are possible, reducing the probability of a planet being captured on an orbit like that proposed