The Vulcan Affair – 22nd November 2017

Our arranged speaker Jeff Wagg was unable to attend November’s society meeting, so Tony Sizer stepped in to talk on ‘The Vulcan Affair’.

Tony started by taking us back to the 1878 USA eclipse and comparing it with the recent 2017 USA eclipse and the vast differences in prevailing conditions. Whilst eclipse seekers in 2017 had modern safe travel and few accommodation problems, competition for viewing locations was substantial given the millions flooding into the best viewing areas; whereas in 1878, travel was difficult and accommodation mostly non-existent or poor and, in the best viewing areas, unsafe due to Indians. However, few people knew or cared that the eclipse was happening. However, on top of the eclipse was the potential to find the proposed existence of the planet ‘Vulcan’.

Tony then segued nicely across to talk about the discovery of Uranus by Sir William Herschel in 1781 continuing on to the discovery of Neptune. This planet, although possibly plotted by Galileo as far back as 1612, was proposed as an unknown celestial body by the noting of deviations to the tables outlined by Alexis Bouvard in 1821. Tony then outlined the story of the final discovery of Neptune by both John Couch Adams and Urbain Le Verrier. I won’t go into the full story here but suffice to say that is a good read if you get the chance.

It was here that I really enjoyed the talk as, although I was familiar with the story, Tony was able to provide a more personal touch to the intrigue and machinations that took place between both men and their respective countries. One result was that for quite some time, about 70 years, Neptune was known as ‘George’s Star’ or even, in France, ‘Le Verrier’. Finally, common sense prevailed and Neptune became the internationally known name.

Segueing nicely again, Tony talked of the interest then placed on the perturbations of Mercury and whether this planet was being influenced by an ‘unknown planet’, which was to become known as ‘Vulcan’. Le Verrier became convinced that such an unknown planet existed; his theories seemingly supported by a number of alleged sightings by transit of the Sun on previous occasions from observers around the world.

This led us back then to the American eclipse of 1878 when the obvious opportunity to confirm or deny the existence of this ‘planet’ could be determined. Regrettably the two observers of note, James Craig Watson and Lewis Swift both confirmed an erroneous sighting! Le Verrier continued to believe in the existence of this planet until he died in 1877, although no conclusive proof ever became known.

Finally, in 1915, Einstein’s theories explained the Mercury orbital peculiarities as perihelion precession; and all was resolved.

Thanks again Tony for a really interesting talk.

The Hunt for Vulcan, the Planet That Wasn’t There (National Geographic)
Vulcan (hypothetical planet) (Wikipedia)
Neptune (Wikipedia)

Hugh Alford, FRAS
Vice-Chair

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