Vulcan

Neptune was the first planet to be ‘discovered’ by mathematical prediction rather than empirical observation. Following Newton’s work on gravity, astronomers knew that planetary bodies affected one anothers orbits due to the gravitational field of each object working on the things around it.

Unexpected fluctuations in the orbit of Uranus lead to the hypothesis that there must be an undetected planet lying outside of its procession around the Sun and pulling the planet out of its natural motion as they moved closer together.

Urbain Le Verrier, a French astronomer at the Paris Observatory, calculated the position of this celestial object using mathematics and his observations of the discrepancies in the orbit of Uranus against the orbit established by Newton’s laws of gravity.

Le Verrier announced his final predicted position for the unseen planet on August 31st 1846.

The planet was observed for the first time by Johann Galle, a German astronomer at the Berlin Observatory, who used Le Verrier’s prediction to guide his viewing.

Le Verrier’s calculation was within 1 degree of the actual position of the planet that was to become known as Neptune.

At the same time Le Verrier was working on fluctuations in the orbit of Mercury.

Again Le Verrier used the Newtonian model to calculate the effect of gravitation on the movement of Mercury around the Sun and in 1843 published a provisional theory on the existence of a previously undetected planet between the Sun and Mercury that would explain the erratic orbit that Mercury demonstrated.

A transit of Mercury, where the planet would pass across the face of the Sun, would provide an ideal opportunity to spot this new planet and fortunately there was a transit in 1843, shortly after Le Verrier published his prediction.

The transit came and went but no new planet was seen in the area Le Verrier had anticipated it would be. He continued with his work and in 1859 published a more complete study of Mercury’s orbit. This was consisted of modifications to his calculations and more thorough observations based on 14 further transits.

Le Verrier was so confident of his prediction that he suggested the planet should be named ‘Vulcan’ when it was eventually discovered. The Roman god of the forge and fire was an ideal namesake for a planet closer to the Sun than any other previously discovered.

Many observations of the new planet were reported from across the globe by astronomers who used Le Verrier’s calculations, however none of them could ever be confirmed and Vulcan evaded any concrete detection.

Le Verrier died in 1877, still convinced he had discovered a planet that had simply never been seen.

With his death astronomers became less certain of his prediction and observations of the planet died down.

Eventually, in 1915, Albert Einstein published his General Theory of Relativity. This modified Newton’s work and proposed that the size of an object would affect the strength of the objects gravitational field. The Sun, being by far the largest object in the Solar System, simply had a strong enough gravitational field to affect Mercury’s orbit in a manner that Newtonian mechanics would never predict. In reality the mass of the Sun affects all planets in the same way but Mercury’s proximity to the Sun, and the fact that there are no large objects between the Sun and Mercury, simply makes the effect more pronounced.

Le Verrier couldn’t have been more wrong, it was the lack of a planet between the Sun and Mercury that had caused the erratic orbit.

The idea of planet Vulcan never entirely died though.

In 1966 Gene Roddenberry, the creator of a new Science Fiction television show called ‘Star Trek’ needed a fictional home planet for Spock, one of his characters.

Originally Spock was going to be a Martian but Roddenberry felt there was a strong possibility of a manned trip to Mars during the shows run and this would cause the character to lose some of his mystique. To be on the safe side Roddenberry chose the name of a planet that had been the subject of feverish speculation but would never have a man walk upon it.

Spock would be a Vulcan...