William Henry Pickering: The Great Celestial Observer

Astronomer William Henry Pickering with a photograph of the Horsehead Nebula. Public Domain

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.

A portrait of Timothy Pickering as secretary of state, before 1828, by Gilbert Stuart. Public Domain

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.

Astronomer brothers (L) William Henry Pickering, 1909, and Edward Charles Pickering. Library of Congress. Public Domain

During these teaching years, possibly as early as 1882, Pickering began to take celestial photography using dry plates. As he became more proficient in dry plate photography, his photos would have profound effects on the astronomical community.

Searching California

During Pickering’s final year teaching at MIT, the Harvard Observatory received a large donation from the Boyden Fund with the intention to build a new observation station. Pickering seemed to be just the person to find a new locale for it.

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.

Photograph of the Jan. 1, 1889 solar eclipse from Norman, Calif. Public Domain

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.”

With this proposed location for the Boyden Station, Harvard College Observatory hoped to compete with the University of California’s recently opened Lick Observatory, located on Mount Hamilton along Diablo Range. The construction of the station, however, met with setbacks and hardships, specifically during the winter of 1889–90. After about 18 months, they abandoned the location. Mount Wilson Observatory was later built on this site.

How About Peru?

The year of that harsh winter in 1889, Edward sent Solon Bailey to South America to find a location for the Boyden Station. After two years, Bailey chose Aréquipa in southern Peru. The city resides at an elevation of more than 7,000 feet, surrounded by three volcanoes. Edward chose Pickering to oversee the construction of the Boyden Station, and then remain there as its director.

Although Edward wanted the station to relay spectrographic and photometric data to Harvard, Pickering was interested in studying Mars during its opposition—an event that takes place approximately every 26 months. In 1892, Pickering reestablished communication with the New York Herald, relaying his observations. Throughout the year, sans a gap between July 9 and Sept. 24, Pickering studied Mars every night, creating 373 drawings of the planet’s various features. But this wasn’t the purpose of his appointment. His brother, frustrated with Pickering’s research and lack of communication, recalled him to Massachusetts.

Back to America

A portrait of astronomer Percival Lowell in 1904. Library of Congress. Public Domain

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.

Lowell Observatory in Flagstaff, Arizona. Library of Congress. Public Domain

After helping Lowell with his telescope, but before his ninth planet contribution, Pickering made an interesting observation near Saturn. Although Pickering had been fired by his brother from his position at the Boyden Station, he could still study the information coming in from Peru. In 1899, upon a thorough study of the dry plates taken around Saturn, Pickering noticed something moving in retrograde motion around “The Ringed Planet.” Pickering had discovered Saturn’s ninth moon. He named it Phoebe, after the Greek Titan goddess. Phoebe was the first moon discovered by a photograph.

Jamaica and Planet O

The same year as his Saturn moon discovery, Pickering was sent to Jamaica to establish another observatory. His work there would be groundbreaking and exhaustive. Pickering selected the city of Mandeville. Toward the end of 1900, Pickering installed in the observatory a large telescope: 135-foot focal length with a 12-inch aperture.

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.”

Frontispiece of the full moon from "The Moon: A Summary of the Existing Knowledge of Our Satellite," 1903, by William Henry Pickering. Internet Archive. Public Domain

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.

Percival Lowell observing planets with the 24-inch Alvan Clark & Sons refracting telescope at the Lowell Observatory in 1914. Public Domain

In 1911, Pickering decided to make Jamaica his home, although he returned to the United States on occasion. Over the next 27 years at the Mandeville Observatory, he studied the planets, Jupiter’s satellites, and the moon. He retired from academia in 1924, but from 1914 to 1930, his work was consistently published in Popular Astronomy (an American magazine published from 1893 to 1951; not to be confused with the UK magazine of the same name).

Mountains, Societies, and Awards

A photograph of Horsehead Nebula by William Henry Pickering in 1888. Public Domain

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.

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