He was the University of Michigan’s “brightest son.”

That’s what Acting President Henry Simmons Frieze said of the gifted 19th century astronomer, James Craig Watson.

Watson discovered 22 asteroids between 1863-77. He drew honors from around the world, including the prestigious Lalande Prize from the French Academy of Sciences.

Then, on a viewing trip to Wyoming in 1878 during a solar eclipse — Thomas Edison traveled with him — Watson was sure he’d observed Vulcan, the rumored planet revolving within Mercury’s orbit.

Victorian-era astronomers anticipated its presence, due to irregularities in Mercury’s orbit. As the Chicago Daily Tribune noted, “Prominent astronomers have changed front more than once from disbelief to belief and back to disbelief again in (Vulcan’s) existence.”

Watson was the first professional astronomer to report seeing such a planet, and record observations.

“Live long and prosper” is the traditional salutation spoken by citizens of the fictional planet Vulcan, of today’s Star Trek lore. But while Watson prospered — his reputation in astronomy circles soared, and his abilities with numbers served him well in business — he did not live long.

Nearly one year after he’d reluctantly left U-M and its Detroit Observatory for a new, better observatory at the University of Wisconsin, Watson died unexpectedly. He had hoped to better observe Vulcan and record more extensive calculations. Instead, his death in 1880, two years after his triumphant Vulcan discovery, stunned friends and colleagues in Ann Arbor.

“The university is in mourning. She has lost the foremost and brightest of all her sons. This community, this state, the whole world of science mourns his loss. A great light has gone out forever,” Frieze said at Watson’s memorial service in Ann Arbor.

Watson was born in 1838 in Fingal, Ontario, west of London. His talents with mathematics showed early, as he helped his father with intricate assessment rolls at age 9.

The family moved to Ann Arbor when he was 12. In “The Memoirs of James C. Watson,” presented before the National Academy in 1888, George C. Comstock – a former student who became a colleague at Wisconsin – wrote that an important consideration for the move was expanding the boy’s education.

His father was hired at a small factory and Watson also worked there. The boy was chosen to replace the engineer at the factory when he demonstrated he could work the engine better. On breaks, he would study from a Latin or Greek textbook. But the factory closed, and Watson sold apples at the Ann Arbor train station.

He entered school at age 13. “But at the end of the first half day the relations of teacher and pupil were interchanged; the boy withdrew from school and the master came to him for instruction in algebra and geometry,” Comstock wrote. He also worked at trades practiced in the village and became a skilled machinist.

Upon entering U-M at 15, “his facility in translation was greater than most professors of Latin and Greek,” Frieze wrote.

Franz Brunnow, the first chair of astronomy and director of U-M’s new Detroit Observatory, interested Watson in astronomy. He began working in the observatory as a junior. Watson’s mechanical talent came in handy when he built a 4-inch telescope, grinding and polishing the glass. Following graduation, Watson led the observatory when Brunnow left in 1859, but transferred to chair of physics when Brunnow returned the following year.

When Brunnow left for good in 1863, Watson became professor of astronomy and observatory director.

Over the next 15 years, Watson wrote dozens of papers including “Theoretical Astronomy,” a textbook praised by sources including Urbain Le Verrier, the French astronomer known for his role in discovering Neptune.

From 1875-77, Watson taught 129 seniors, juniors and sophomores. Frieze described Watson as patient and encouraging of students with lesser talent than he. Yet some students complained that Watson made it difficult to get into the observatory, as he didn’t want his work there disturbed.

“So long as the university advertises to allow admission to the observatory, it might be well to make the means of gaining this entrance a little more practical,” the student-run University Chronicle reported.

Watson was a member of government eclipse expeditions to Iowa in 1869 and to Sicily in 1870. In 1874 he embarked on a 15-month trip around the world to observe the transit of Venus. He spent several weeks in Egypt, helping to establish a geodetic survey and make accurate measurements of the pyramids. He was made Knight Commander of an honorific order in Egypt and Turkey.

Watson was also in charge of the 1878 government expedition to Wyoming that made headlines.

A photo taken on the trip to Wyoming shows Watson with a group of men and women, and includes Edison. He describes the moment of discovery of two intra-mercurial planets on July 29, 1878, in notes collected in a folder at the Bentley Historical Library.

“At the Mercury total eclipse of the sun I was occupied exclusively in a search for any intra-mercurial planet which might be visible,” he wrote. His measuring and transit recording instruments included circles of hard wood and cardboard, a sharp pencil, and a telescope with a magnifying power of 45.

“Immediately after the commencement of totality I began sweeps east and west,” he wrote. Then, during one sweep, he came across a body “which shone with a muddy light. … I noticed particularly that the object in question did not present any elongation as would be probable were it a comet in that location.”

Watson went on to detail the declination beyond the sun of the object, “which I believe to be an intra-mercurial planet.”

Specifically, the elusive planet Vulcan.

There was skepticism but also congratulations from colleagues. Viewing the same eclipse from Denver, Lewis Swift – the leading astronomer of the time – saw one of the objects and said Watson had beaten him to discovering Vulcan by two minutes, the interval between total eclipse in Wyoming and Colorado.

Writers at the Washington Post were quick to hold up Watson’s discovery as scientifically sound given the astronomer’s history of detecting new comets and asteroids. “Accustomed as he has been for so many years to spy out these objects, it is not at all probable that he could be mistaken as to the nature of the object seen,” the paper asserted. “His reputation as an observer will cause the statements which he made to be generally received, and we must add Le Verrier’s Vulcan to our solar system”

Watson wrote of his planetary discoveries in the American Journal of Science and in the Astronomische Nachrichten. He remained focused on Vulcan and sought to continue his observations. When the opportunity to become director of a new, better-equipped observatory at the University of Wisconsin at an annual salary of $3,000 was offered, Watson left Ann Arbor to continue his observations of the intra-mercurial planet.

But in November 1880 his star dimmed. He caught pneumonia and died. He was 42.

Watson’s discovery of Vulcan was ultimately discounted, as further observations failed to turn up a body of significant size. By the early 20th century, the astronomical community believed irregularities in Mercury’s orbit were well explained by Einstein’s theory of general relativity, published in 1915.

Nevertheless, Watson’s observations at the 1878 eclipse have never been fully explained, wrote William Sheehan and Richard Baum, co-authors of In Search of Planet Vulcan: The Ghost in Newton’s Clockwork Universe.

Fifty years after Vulcan, U-M Observatories Director Heber D. Curtis said it was inconceivable that an astronomer of Watson’s experience could have made a mistake.

“In the history of American astronomy in the 19th century, Watson occupies a very prominent and honored place, and his rank seems secure,” Curtis wrote.

In his eulogy of Watson, Frieze said, “Yes, our astronomer has inscribed his name with those of Galileo, and Herschel and Le Verrier, on tablets which must endure as long as man shall continue to gaze upon the heavens, and to study the wonders they reveal.”

Watson’s name and reputation outlasted his erroneous discovery. His bequest to the National Academy of Sciences established the James Craig Watson Medal, which has been presented for more than 125 years. Recipients are awarded a $25,000 prize and $50,000 to support their research in astronomy.

Watson is buried in Forest Hill Cemetery in Ann Arbor.

A version of this story originally appeared in the University Record in January 2015, and is reprinted with permission. Sources include the James Craig Watson papers at the Bentley Historical Library; Michigan Alumnus Quarterly Review (summer 1938); National Academy of Science records; and contemporary news accounts.