I know what might be going through your mind, after noting the title of today’s post. Complete with the “Star Trek” theme song and images of Leonard Nimoy would be the fictional planet of teevee and movie fame. No, this is not what I have in mind. Today’s planetary subject is also one that doesn’t actually exist. The discovery of this hypothetical planet was announced 154 years ago, today.
In the mid-19th Century, French mathematician, Urbain Le Verrier, set to work on the peculiarities of the planet Mercury’s orbit around our Sun. Scientists at the Paris Observatory wished to construct an orbital model based upon Sir Isaac Newton’s Laws of Motion and Gravitation.
Le Verrier’s first try was put to the test during one of Mercury’s transits across the face of the Sun in 1843. His hypothesis failed to match his predictions during actual observations by astronomers.
The observations showed that Mercury’s perihelion advanced very slightly during each orbital pass. This orbital motion is known, technically, as “perihelion precession. In this case, the classical Newtonian mechanics prediction was off by some 43-arc-seconds per 100 years.
The mathematician believed the discrepancy would be explained by the presence of a planetary body orbiting between Mercury and the Sun. Le Verrier’s proposed name for this hypothetical planet was “Vulcan”. The name coming from the Roman god of fire and volcanoes. The name respected the tradition of naming planets after Roman Gods.
On March 26, 1859, physician Edmond Lescarbault of Orgeres, France reported his observation of an unknown, planet-size object crossing the face of the Sun. Dr. Lescarbault told Le Verrier that he estimated the transit’s duration to be more than one and a quarter hours or approximately 1:17:09. Le Verrier believed the testimony of the country doctor.
Le Verrier took the doctor’s data and calculated the orbit of Vulcan and reckoned an orbital distance of 21,000,000 kilometres with an orbital duration of 19 days, 17 hours long.
On January 2, 1860, Urbain Le Varrier, presented his report and findings about the planet Vulcan to a gathering of the Academie des Sciences in Paris. The report was met with strong skepticism by reknowned astronomer, Emmanuel Liais. The astronomer strongly disputed the passage of any object across the Sun’s disc at the time of Lescarbault’s reported sighting.
Liais reported that he had been observing and noting the solar surface with his telescope that was twice as powerful as that used by Dr. Lescarbault. Liais reiterated that nothing passed between him and the Sun at the specified time.
Meantime, Le Verrier published the predicted dates of Vulcan’s transits. But nothing ever again showed up to any astronomical observers. For several decades, astronomers resumed their searches for Vulcan. Some false reports turned out to be round sunspots that moved across the solar surface, mimicking the transits of a planet. There was some hope that Vulcan might be seen during a full eclipse of the Sun. Nothing unusual was seen by anybody during that event, either.
It took Albert Einstein’s Theory of General Relativity, in 1915, to explain Mercury’s orbit. Einstein’s calculations exactly predicted the advance of Mercury’s perihelion precession. There was no longer any need for another planetary object like Vulcan to explain the anomaly.
artist’s rendition of Mercury with Vulcanoid objects
While the vast majority of astronomers were convinced of the accuracy of Einstein’s findings, there were a few, who wanted to verify the calculations with their own observations. One of those scientists was Henry Courten of New York’s Dowling College. Courten analyzed the photographs of the 1970 total solar eclipse. He claimed to have found several small objects at a close distance from the Sun. He reported that there is an intra-Mercurial, planet-like object in orbit around the Sun.
Nobody has ever verified Courten’s claims, but some astronomers believe that there is a possibility that small objects, or Vulcanoids, might exist between Mercury and the Sun, but none would be bigger than 6-kilometres across.
Nothing of that size could affect Mercury’s perihelion precession to any extent. No reputable scientist nor academic institution has detected Vulcan.
Ciao
The Blue Jay of Happiness thanks NinePlanets.org for background information.
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