William Henry Pickering: The Great Celestial Observer

William Henry Pickering (1858–1938) was born in Boston to a prominent American family, one whose roots went back to 1636. Arguably, the most prominent member in the Pickering lineage was his great-grandfather, Timothy Pickering (1745–1829), who had been a colonel, adjutant general, quartermaster general, and a member of the Board of War during the American Revolution. He served as a delegate during the 1787 Constitutional Convention. In the new republic, he was a representative, senator, postmaster general, secretary of war, and secretary of state. The fame of his descendant William Henry Pickering, would not be among American politicians, but rather among the stars—literally.
By the time Pickering began attending Massachusetts Institute of Technology (MIT), his older brother Edward (1856–1919) had been a physics professor at the school for a decade. Shortly after Pickering’s arrival at MIT, Edward was appointed professor of astronomy at Harvard College. It was the same school Timothy Pickering had graduated from more than a century prior. Edward was also appointed director of the Harvard College Observatory, a position he held for more than 40 years and one that would greatly benefit his younger brother.
William Henry Pickering graduated from MIT in 1879 and was hired there as a physics professor the following year. He remained in that position until 1887 when he was hired as an assistant professor of astronomy at Harvard and was brought on staff at the Harvard College Observatory.
At the end of 1888, Pickering led a scientific expedition to California in order to observe the solar eclipse, which was to take place on New Year’s Day 1889. During this expedition, Pickering and his elder brother, Edward, who had remained at Harvard, collaborated with the New York Herald to relay information about the team’s findings.
While on the lookout for an observation point, Pickering and his team, which included optician Alvan Clark, visited Mount Wilson, one of the peaks in the San Gabriel Mountains. He proposed Mount Wilson to Harvard as the place for “the largest and finest telescope in the world.”
After Pickering returned, he made the acquaintance of wealthy businessman and amateur astronomer, Percival Lowell. Pickering assisted Lowell in establishing his own observatory in Flagstaff, Arizona. Lowell was a Mars enthusiast, who would become famous for claiming to have seen canals on Mars—canals created by an intelligent life form. This claim was soon disproven. More importantly, Lowell theorized the possibility of a ninth planet in the solar system, a theory in which Pickering would play a significant role substantiating.
The following year, he studied the moon extensively, taking about 80 dry plate photographs and notating each one. These 80 dry plates were categorized into 16 districts of the moon with five images per district based on the phases of the moon. The result of this work was the first photographic atlas of the moon. It was published as a book in 1903, entitled “The Moon: A Summary of the Existing Knowledge of our Satellite.”
Pickering agreed with Lowell’s theory that a ninth planet existed. He actually believed there were possibly seven more in the solar system. The two men predicted possible locations for what Lowell called Planet X and what Pickering called Planet O. Lowell died in 1916, 14 years before the discovery of Pluto (that is, Planet X and Planet O). Lowell received credit for the discovery, specifically because Clyde Tombaugh discovered it at the Lowell Observatory.
Pickering apparently had no problem with Lowell being given credit, though he was certain to clarify that his predictions were much closer to Pluto’s exact location than Lowell’s.
Pickering chose mountains and peaks as observation points for obvious scientific reasons, but there seems to be another reason he preferred them. Pickering was a great mountain climber. He climbed the Half Dome at Yosemite, El Misti in Peru, and about 100 other mountains throughout the globe.
Pickering wrote several works alongside his Popular Astronomy articles and his photographic book about the moon, including “Walking Guide to the Mt. Washington Range,” “Investigations in Astronomical Photography,” “Visual Observations of Sun and Moon,” “Visual Observations of Moon and Planets,” “Search for Planets Beyond Neptune,” “Statistical Investigations of the Cometary Orbits,” and “Reports on Mars.”
He was also a member of several scientific societies, including the American Academy of Arts and Sciences, American Astronomical Society, the British Astronomical Society, Royal Astronomical Society, the Astronomical Society of Mexico, and the Astronomical Society of the Pacific. He was awarded the Lalande Prize in 1905 and the Janssen Medal in 1909 from the French Academy of Sciences, two medals from the Astronomical Society of Mexico, and was elected as Chevalier of the Order of St. James in Portugal.
For a man who focused so much on the heavens, it seems appropriate that several celestial areas were named in his honor. These sites include craters on the moon and on Mars. He and his brother shared the naming honor for asteroid 784 Pickeringia.