Vulcan (hypothetical planet)
By 1859 he had confirmed unexplained peculiarities in Mercury's orbit and predicted that they had to be the result of the gravitational influence of another unknown nearby planet or series of asteroids.
A French amateur astronomer's report that he had observed an object passing in front of the Sun that same year led Le Verrier to announce that the long sought after planet, which he gave the name Vulcan, had been discovered at last.
[7] Proposals that there could be planets orbiting inside Mercury's orbit were put forward by British scientist Thomas Dick in 1838[8]: 264 and by French physicist, mathematician, and astronomer Jacques Babinet in 1846 who suggested there may be "incandescent clouds of a planetary kind, circling the Sun" and proposed the name "Vulcan" (after the god Vulcan from Roman mythology) for a planet close to the Sun.
German amateur astronomer Heinrich Schwabe searched unsuccessfully on every clear day from 1826 to 1843 and Yale scientist Edward Claudius Herrick conducted observations twice daily starting in 1847, hoping to catch a planet in transit.
[8]: 264 French physician and amateur astronomer Edmond Modeste Lescarbault began searching the Sun's disk in 1853, and more systematically after 1858, with a 3.75 inch (95 mm) refractor in an observatory he set up outside his surgery.
[8]: 146 In 1840, François Arago, the director of the Paris Observatory, suggested to mathematician Urbain Le Verrier that he work on the topic of Mercury's orbit around the Sun.
He calculated that it was either another Mercury size planet or, since it was unlikely that astronomers were failing to see such a large object, an unknown asteroid belt near the Sun.
On 2 January 1860 he announced the discovery of the new planet with the proposed name from mythology, "Vulcan",[16] at the meeting of the Académie des Sciences in Paris.
[20] An American observer, Richard Covington, many years later claimed to have seen a well-defined black spot progress across the Sun's disk around 1860 when he was stationed in Washington Territory.
Then, during the total solar eclipse of July 29, 1878, two experienced astronomers, Professor James Craig Watson, the director of the Ann Arbor Observatory in Michigan, and Lewis Swift, from Rochester, New York, both claimed to have seen a Vulcan-type planet close to the Sun.
Watson reported that it had a definite disk—unlike stars, which appear in telescopes as mere points of light—and that its phase indicated that it was on the far side of the Sun approaching superior conjunction.
The idea that four objects were observed during the eclipse generated controversy in scientific journals and mockery from Watson's rival C. H. F. Peters.
Peters noted that the margin of error in the pencil and cardboard recording device Watson had used was large enough to plausibly include a bright known star.
"[26] In 1915 Einstein's theory of relativity, an approach to understanding gravity entirely differently from classical mechanics, removed the need for Le Verrier's hypothetical planet.
Einstein's theory was empirically verified in the Eddington experiment during the solar eclipse of May 29, 1919 when photographs showed the curvature of spacetime was bending starlight around the Sun.
Astronomers generally quickly accepted that a large planet inside the orbit of Mercury could not exist, given the corrected equation of gravity.
