Urbain Le Verrier

In 19^th century Europe, Le Verrier became a celebratory, at least within scientific circles. Now, virtually unknown amongst the British and maybe fading from the collective memory even in his native France. Certainly, a sage, who exhibited skills in chemistry and mathematics, but a resilient scholar, both an unrelenting researcher and a demanding teacher.

From childhood, Le Verrier was demonstrably exceptional, a talented student with a supportive father. Brought up in Normandy within a family of modest means, in 1831 CE, aged 20, he was admitted to a pre-eminent scientific institution, the École Polytechnique, in Paris. Despite displaying a flair for mathematics, one of the country’s best students, he pursued chemistry for two years under the top teachers in France.  His father sold the family home to fund his son’s studies.

After graduating, he spent two years in industry, researching the interaction of phosphorous with, respectively, oxygen and hydrogen. Relevant to the tobacco industry, because matches were produced using phosphorous. He published two papers and earned plaudits from distinguished chemists, leading to job offers in provincial France.

While these may have been attractive, Le Verrier preferred research in Paris, supporting himself by teaching. His motivation was a hankering for the École Polytechnique, an environment he had enjoyed. In 1836 CE, a vacancy for a chemistry tutor or répétiteur arose; he applied, maybe believing he was likely to win the position. Disappointment ensued.

Undeterred, when another opening surfaced, he again applied, despite the role being within the astronomy discipline. Success: he was appointed. While it might seem odd that an industrial chemist was recruited to teach astronomy, there were probably several factors. The Polytechnique knew his abilities, his recently published papers had gained him kudos, and he was recognised as a skilled mathematician. This last point was maybe the most significant.

Here, our story commences. Self-confidence is a trait manifest in Le Verrier’s career. His role as an academic began accordingly, both in research and teaching. He soon became an admissions adjudicator, a position of responsibility. In 1839 CE, his first astronomical paper addressed the stability of the Solar System. He followed this with a study of comets, demonstrating that apparently unrelated sightings were of the same object, trajectories being influenced by Jupiter’s gravity. These insights were well-received, resulting in accolades including admission to the French Academy. Now, a national figure.

His presence at the Paris Observatory, where he spent much of his time, provoked both admiration and scorn. A remorseless drive for improved performance was resented by the staff; some resigned, many detested him. Le Verrier was untroubled.

In 1845 CE, he began an analysis of irregularities in Uranus’s orbit and proved that they were not attributable to known planets. He speculated that an unidentified planet beyond Uranus could account for the perturbations. His mathematical treatment of the question required the computation of 469 discrete terms, an undertaking he undertook manually. No digital computers, not even a calculator, in his day. In September 1846 CE, he wrote to a fellow astronomer, Johann Galle, at the Berlin Observatory, asking him to search for an object at a position he specified.

Two points are noteworthy. Although both astronomers, Le Verrier was a theoretician while Galle’s specialism was observational studies. Secondly, it seems that Berlin became involved because of Le Verrier’s disquiet over the Paris Observatory’s performance.

Galle, while perhaps doubtful about the request, initiated a search for the mysterious body. He found it on the first night of observing, within 1° of the predicted position. He confirmed the sighting on the next night before responding to Le Verrier. A planet had been uncovered, attributable to Le Verrier’s mathematics and Galle’s observational skills.

Francois Arago, then Le Verrier’s boss, described his achievement as ”one of the most magnificent achievements of theoretical astronomy”. A master of celestial mechanics, certainly, but perhaps one with an innate sense for the heavens.

In London, on 01 October, the headline in the Times straightforwardly announced “Le Verrier’s planet found.” Inevitably, honours and recognition. The Royal Society awarded a medal. In Paris, a professorship was created at the Sorbonne especially for Le Verrier.

A designation was internationally agreed and confirmed by the end of the year. The planet’s blue colour, which we now know as a feature of methane atmospheres, hinted at oceans, so a god of the sea maintained the custom of naming planets (except Earth) after Roman deities: Neptune.

Still a young man, Le Verrier’s energy and poise propelled him onwards, ricocheting from one challenge to the next. Reforming mathematics courses at École Polytechnique caused controversy but left him unperturbed by the resultant opprobrium.

Astronomically, his ambition was to address the entire planetary system, “putting everything in harmony if possible.” The last two words hint at humility. His outstanding work led to two more medals from London, from the Royal Astronomical Society, for his work on the inner planets, and later, the outer planets.

A footnote to these studies was the puzzlement over perplexing deviations in the orbit of Mercury, the innermost planet. Many were convinced that only a body even closer to the Sun could explain the variances. Astronomers searched in vain for this furtive planet, which was labelled Vulcan. Only later, in 1915 CE, after Le Verrier’s life, did General Relativity rationalise the phenomenon, thanks to Albert Einstein.

Vulcan, though, has entered popular culture through the inscrutable Mr Spock. Much better known today than either Le Verrier or Galle.

RNP – while an obscure figure now, Le Verrier will be a star in my threequel to Jimbo’s Assumption. As one of his peers asserted, “he discovered a planet with the point of his pen.” 

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