Jan 022018

No, I am not talking about Spock’s home planet, I am talking about a planet that was hypothesized to lie in an orbit between Mercury and the Sun which had been dubbed Vulcan by astronomers of the time.  On this date in 1860, Urbain Le Verrier, chief proponent of the existence of Vulcan, announced the discovery of Vulcan, based on observations by amateur astronomer, Edmond Modeste Lescarbault, to a meeting of the Académie des Sciences in Paris.  Subsequently, a number of reputable investigators became involved in the search for Vulcan, but no such planet was ever found. Rather, the peculiarities in Mercury’s orbit that led to Le Verrier’s hypothesized planet, have now been accounted for by Albert Einstein’s theory of general relativity. Here we have a clear case of seeing something that’s not there because you are convinced it ought to be – the opposite phenomenon of failing to see something within your field of vision because you are convinced it does not exist (a well known and well documented phenomenon).

In 1840, François Arago, the director of the Paris Observatory, suggested to Le Verrier, a French mathematician, that he work on the topic of the planet Mercury’s orbital motion around the Sun. The goal of this study was to construct a model based on Sir Isaac Newton’s laws of motion and gravitation. By 1843, Le Verrier published his provisional theory on the subject, which would be tested during a transit of Mercury across the face of the Sun in 1843. As it turned out, predictions from Le Verrier’s theory failed to match the observations. Le Verrier renewed his work and, in 1859, published a more thorough study of Mercury’s motion. This was based on a series of meridian observations of the planet as well as 14 transits. The rigor of this study meant that any differences from observation would be caused by some unknown factor. Indeed, there still remained some discrepancy. During Mercury’s orbit, its perihelion advances by a small amount each orbit, technically called perihelion precession. The phenomenon is predicted by classical mechanics, but the observed value differed from the predicted value by the small amount of 43 arcseconds per century.

Le Verrier postulated that the excess precession could be explained by the presence of a small planet inside the orbit of Mercury, and he proposed the name “Vulcan” for this object. In Roman legend, Vulcan was the god of both beneficial and hindering fire, including the fire of volcanoes, making it an apt name for a planet so close to the Sun. Le Verrier’s recent success in discovering the planet Neptune using the same techniques lent strong credence to his claim, and astronomers around the world attempted to observe a new planet there, but nothing was ever found.

Lescarbault’s observatory

On 22 December 1859, Le Verrier received a letter from French physician and amateur astronomer Edmond Modeste Lescarbault, who claimed to have seen a transit of the hypothetical planet earlier in the year. Le Verrier took the train to the village of Orgères-en-Beauce, 70 kilometers (43 mi) southwest of Paris, where Lescarbault had built himself a small observatory. Le Verrier arrived unannounced and proceeded to interrogate Lescarbault. Lescarbault described in detail how, on 26 March 1859, he noticed a small black dot on the face of the Sun, which he was studying with his modest 3.75 inch (95 mm) refracting telescope. Thinking it to be a sunspot, Lescarbault was not at first surprised, but after some time had passed he realized that it was moving. Having observed the transit of Mercury in 1845, he guessed that what he was observing was another transit, but of a previously undiscovered body. He took some hasty measurements of its position and direction of motion, and using an old clock and a pendulum with which he took his patients’ pulses, he estimated the duration of the transit at 1 hour, 17 minutes and 9 seconds (much too fast to be a sunspot).

Le Verrier was satisfied that Lescarbault had seen the transit of a previously unknown planet. Thus on January 2nd, 1860 he announced the discovery of Vulcan to a meeting of the Académie des Sciences in Paris. Lescarbault, for his part, was awarded the Légion d’honneur and invited to appear before numerous learned societies. Not everyone accepted the legitimacy of Lescarbault’s “discovery,” however. An eminent French astronomer, Emmanuel Liais, who was working for the Brazilian government in Rio de Janeiro in 1859, claimed to have been studying the surface of the Sun with a telescope twice as powerful as Lescarbault’s at the very moment that Lescarbault said he observed his mysterious transit. Liais, therefore, was “in a condition to deny, in the most positive manner, the passage of a planet over the sun at the time indicated.”

Based on Lescarbault’s “transit”, Le Verrier computed Vulcan’s orbit: it supposedly revolved about the Sun in a nearly circular orbit at a distance of 21 million kilometers (0.14 AU; 13,000,000 mi) The period of revolution was 19 days and 17 hours, and the orbit was inclined to the ecliptic by 12 degrees and 10 minutes (an incredible degree of precision). As seen from the Earth, Vulcan’s greatest elongation from the Sun was 8 degrees. Numerous reports—all of them unreliable—began to reach Le Verrier from other amateurs who claimed to have seen unexplained transits. Some of these reports referred to observations made many years earlier, and many could not be properly dated. Nevertheless, Le Verrier continued to tinker with Vulcan’s orbital parameters as each new reported sighting reached him. He frequently announced dates of future Vulcan transits, and when these failed to materialize, he tinkered with the parameters some more.

Among the earlier alleged observers of Vulcan, the following are the most noteworthy:

Capel Lofft reported ‘an opaque body traversing the suns disc’ on 6 January 1818.

Baron Franz von Gruithuisen, on 26 June 1819, reported seeing “two small spots…on the Sun, round, black and unequal in size”

J.W. Pastorff, on 23 October 1822, 24 and 25 July 1823, six times in 1834, on 18 October 1836, 1 November 1836 and on 16 February 1837, also claimed to have seen two spots; the larger was 3 arcseconds across, and the smaller 1.25 arcseconds.

Shortly after 8 o’clock on the morning of 29 January 1860, F. A. R. Russell and three other people saw an alleged transit of an intra-Mercurial planet from London. A US 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. No “observations” of Vulcan were made in 1861. Then, on the morning of 22 March 1862, between 8 and 9 o’clock GMT another amateur astronomer, a Mr Lummis of Manchester, England, saw a transit. His colleague, whom he alerted, also saw the event. Based on these two men’s reports, two French astronomers, Benjamin Valz and Rodolphe Radau, independently calculated the object’s supposed orbital period, with Valz deriving a figure of 17 days and 13 hours and Radau a figure of 19 days and 22 hours. On 8 May 1865 another French astronomer, Aristide Coumbary, observed an unexpected transit from Istanbul.

Between 1866 and 1878 no reliable observations of the hypothetical planet were made. Then, during the total solar eclipse of 29 July 1878, two experienced astronomers, Professor James Craig Watson, the director of the Ann Arbor Observatory in Michigan, and Lewis Swift, an amateur from Rochester, New York, both claimed to have seen a Vulcan-type planet close to the Sun. Watson, observing from Separation, Wyoming, placed the planet about 2.5 degrees southwest of the Sun and estimated its magnitude at 4.5. Swift, who was observing the eclipse from a location near Denver, Colorado, saw what he took to be an intra-mercurial planet about 3 degrees southwest of the Sun. He estimated its brightness to be the same as that of Theta Cancri, a fifth-magnitude star which was also visible during totality, about 6 or 7 minutes from the “planet.” Theta Cancri and the planet were very nearly in line with the center of the Sun.

Watson and Swift had reputations as excellent observers. Watson had already discovered more than 20 asteroids, while Swift had several comets named after him. Both described the color of their hypothetical intra-mercurial planet as “red”. 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 approaching superior conjunction.

These are merely the more “reliable observations” of alleged intra-Mercurial planets. For half a century or more, many other observers tried to find the hypothetical Vulcan. Many false alarms were triggered by round sunspots that closely resembled planets in transit. During solar eclipses, stars close to the Sun were mistaken for planets. At one point, to reconcile different observations, at least two intra-mercurial planets were postulated.

In 1877 Le Verrier died, convinced to the end of having discovered another planet. With the loss of its principal proponent, however, the search for Vulcan abated. After many years of searching, astronomers were seriously doubting the planet’s existence. By 1915, Einstein’s theory of relativity, an entirely different approach to understanding gravity from classical, Newtonian mechanics, solved the problem. His equations predicted the observed amount of advance of Mercury’s perihelion precisely, without any recourse to the existence of a hypothetical Vulcan. The new theory modified the predicted orbits of all planets, but the magnitude of the differences from Newtonian theory diminishes rapidly as one gets farther from the Sun. Also, Mercury’s fairly eccentric orbit makes it much easier to detect the perihelion shift than is the case for the nearly circular orbits of Venus and Earth. Case closed. Vulcan does not exist. Someone needs to tell Mr Spock.

It’s a little odd to come up with a recipe to celebrate something that does not exist, but there is a little glimmer. Today is Cream Puff Day in the US. Cream puffs look a little like odd planets, and I used to love them as a boy when women at my church used to make them for “bring a basket” tea parties. Cream filled choux pastry? What’s not to love. In France, cream puffs are called profiteroles and differ only from their Australian/US cousins in being drizzled with chocolate (and sometimes filled with pastry cream rather than whipped cream – like a planet-shaped éclair).  Since Le Verrier was French, profiteroles it is. Actually, I’ve mostly covered choux paste filled with crème pâtissière   here, https://www.bookofdaystales.com/st-honore-of-amiens/  The recipe there was more complex, though. Consider this a simplified re-run.



Choux pastry

250ml (8 fl oz) water
125g (4¼ oz) butter
125g (4¼ oz) plain flour
¼ tsp salt
4 eggs


450ml (16 fl oz) double cream
1 tablespoon caster sugar
½ tsp vanilla extract


75g (3 oz) plain chocolate


Preheat oven to 230˚C/450F

In a saucepan over medium heat, bring the water to a boil. Add the butter and stir the mixture as it melts, then return it to the boil. Add the flour and salt all at once and stir vigorously until the mixture forms a ball. Remove from the heat and add the eggs, one at a time, stirring vigorously after each egg is added until you have a smooth dough. Spoon the dough (now choux pastry) in heaped tablespoons, 7cm (2 ¾ in) apart, on a baking tray.

Bake 15 minutes in the preheated oven, then reduce the heat to 160˚C/320˚F and bake for 25 more minutes. DO NOT OPEN THE OVEN DOOR (the profiteroles may collapse if the temperature drops suddenly).

Remove the profiteroles from the oven, split them and remove the soft dough from the center. Turn off the oven, f and return the profiteroles to dry in the cooling oven, for 20 minutes more. Then completely cool them on a wire rack.

Whip the cream with an electric mixer until stiff peaks form. Stir in the vanilla and sugar. Fill the profiteroles with whipped cream.  [At this point you have cream puffs.]

Melt the chocolate in a microwave or in a double boiler. Drizzle the melted chocolate over the tops of the profiteroles. Serve immediately. They do not keep long; the choux pastry softens quickly. They also do not keep long when placed in front of me.

Yield: 12 profiteroles