The Lowell Observatory: From Pioneers to Pluto 

Written by Sam Marks

Known as the “Dark Sky City”, Flagstaff, Arizona has differentiated itself from most cities in the United States and the world. Unlike most cities, Flagstaff is one of the few urbanized locations where one can see the night sky very clearly. Due to more than three decades of comprehensive and coordinated legislative efforts, the city reduced light pollution immensely.  

Light pollution is the inappropriate or excessive use of artificial light, often making stars in the night sky invisible to humans. This occurs when a light beam reflects off a surface, such as a pavement or road, or there is a significant glare from light being unfocused on a particular area. This unnecessary use of light creates skyglow, the brightening of a night sky, causing an inability to see stars or planets accurately. The problems caused by light pollution are practically exclusive to industrialized, highly urbanized areas, due to the presence of lights from streetlamps, cars, houses, billboards, or any other luminous objects.  

In 1958, Flagstaff banned large searchlights within city limits. In 1989, a series of laws were introduced that restricted types of lighting to low emission. Additionally, they introduced a series of solar-powered street lights that had fixtures to focus the path of the light directly down and limit glare. In 1999, the Dark Sky Coalition was founded by former US Naval astronomer Chris Luginbuhl and Lance Diskan, who moved to Flagstaff from Los Angeles to ensure his children could grow up seeing the stars at night. This coalition gained massive support from the community, seeing communal rallying around fighting light pollution and, in 2001, Flagstaff was recognized by the International Dark-Sky Society as the world’s first “International Dark Sky City”. These reforms have made Flagstaff one of the most exclusive cities in the world, where one can observe the stars uninterrupted. The great effort from both the local community and government to crack down on light pollution has precedents in Flagstaff’s history of astronomy. 

Prior to its status as the “Dark Sky City”, Flagstaff was known as the “Skylight City”. This is due to Flagstaff being home to the Lowell Observatory, most notable for its discovery of Pluto in 1930. Built in 1894, the Observatory was established by Percival Lowell, a mathematician and astronomer from Massachusetts.  

Lowell had pursued a series of now-discredited theories surrounding different astronomical events; in particular, he was an avid promoter of the theories that Mars once sustained intelligent life. He believed that craters on Mars’ surface were once intricate canals that distributed water across the planet. These ideas were quite popular with the public and Lowell’s theories went on to influence a great number of science fiction writers such as H.G. Wells in The War of the Worlds (1898). However, the lack of scientific backing of these theories saw Lowell discredited among the astronomical community in New England. But his failure to reach the scientific community in New England only saw his research increase. Lowell followed in the footsteps of most who came to America searching for opportunity: he went out west.  

In 1894, Lowell established the Lowell Observatory in Flagstaff, Arizona Territory (this was prior to Arizona’s admission to the US as a state) on the recommendation of fellow astronomer A.E. Douglass. The unincorporated frontier town was chosen for the site of the Lowell Observatory due to its high elevation of 7,000 feet (2,130 meters). Flagstaff was also situated on the east-west transcontinental railroad line, seeing the town grow massively throughout the later 1890s. The strong connections the city had by rail made it easier for Lowell to construct the instruments necessary for observing the sky and space.  

Due to the lack of an established astronomical community in the frontier, Lowell had to improvise in his construction of various facilities of the observatory. To build a telescope dome, Lowell hired Godfrey and Stanley Sykes of the local Sykes Brothers Bicycle Repair Shop. While there were complex differences between the making of bicycles and building a telescope dome, the self-described “makers and menders of anything” took on the task and built the dome. In 1896, Lowell purchased and shipped the $20,000 Clark Refracting Telescope from Alvan Cark & Sons in Boston. Clark & Sons specialized in making lenses for refracting telescopes used in the nineteenth and early twentieth century. The telescope was installed in the Clark Dome and the observatory completed its first building. Carrying on with his astronomical endeavors, Lowell and his team continued to observe the surface of Mars.  

While Lowell’s experimental theories had largely discredited him from the academic communities in New England, the Observatory attracted many now-famous astronomers who supported Lowell’s theories, including brothers Vesto M. and Earl C. Silpher. Migrating to Flagstaff from Mulberry, Indiana, the two brothers made several key discoveries that have become vital to the field. Earl published a Photographic History of Mars (1905-1961) and continued to advocate for the possibility of Mars sustaining life. Vesto has been noted as a pioneer for providing the first empirical basis for the expansion of the universe, all of which would go on to influence Edwin Hubble’s construction of the Hubble Telescope. He later became the director of the Observatory from 1926 to 1952. However, the most notable discovery the Lowell Observatory uncovered was the existence of Pluto.   

Another astronomical theory Lowell developed was the existence of Planet X. Planet X was theorized by observations made of Uranus and Neptune. Both planets have irregular orbits when compared to the rest of the Solar System, leading scientists to question why they might have these discrepancies. The theory proposed by Lowell was that Uranus and Neptune were subject to the gravitational pull of an unobserved, infinitely larger planet that countered the gravitational pull of the Sun. While Lowell would pass away in 1918 before his theory could be researched in more depth, his hypothesis would be taken up by the newly employed Clyde Tombaugh.  

Tombaugh was a self-taught astronomer from Illinois who built his own telescopes with lenses and mirrors. He was hired by the Lowell Observatory in 1929 after sending them incredibly detailed and accurate hand-drawn pictures of Jupiter and Mars. Tombaugh was tasked to search for Planet X, assisted by Elizabeth Williams, the chief computer at Lowell. Prior to mechanical computers, people were employed to perform complex and advanced mathematical calculations. This was one such position that women were incredibly prominent in, and Williams’ calculations were vital to locating where Pluto would be at the time of observation.  

The Astronomer Clyde Tombaugh, Discoverer of Pluto Here Shown with His Homemade 9-Inch Telescope, c. 1930. Image accessed via O’Hara, Elva R. (2006). Clyde W. “Tombaugh: Farm Boy Reached for the Stars.” Borderlands 25. Image cropped from original.

The key instrument Tombaugh used in his analysis was the 13-inch (330 mm) astrograph, a telescope designed for photography, the Observatory had on sight. An astrograph worked by taking pictures of a certain area of space, allowing astronomers to compare pictures of the same area from different months. Tombaugh was able to locate Planet X by comparing photographs of the same stars, which remained in the same positions as previous photographs showed. However, while the stars stayed in the same position, Tombaugh observed that there was an object that changed position since he last took the photos. Taking place on 18 February 1930, this was the discovery of Pluto.  

While not the massive object that Planet X was presumed to be, the discovery of a new planet sent shockwaves through the astronomical community. Tombaugh continued to search for the hypothesized Planet X, but no such planet was or has been discovered. Pluto had been the culmination of experimental scientists who took up work at Lowell. Pluto was even named through unconventional means.  

Coming up with a name for the planet was granted to the public. The winner has been attributed to Venetia Burney, an eleven-year-old girl from England. Her uncle had telegrammed her suggestion to the Lowell Observatory, and it was chosen as the winner. “Pluto” followed the tradition of naming planets after gods and goddesses. Being the Roman god of the underworld, Pluto also had the thematic advantage of being obscured from view, in the same way that Pluto was hidden from observation for quite some time. Lastly, the symbol “PL” for Pluto was also the same initials as Percival Lowell, providing a good way to honor his legacy.  

In 2006, Pluto was demoted to a dwarf planet. This decision has remained controversial to the scientific community and general public. But the ongoing legacy of Pluto has been a cornerstone in the development of Flagstaff as a city. The commitment to fighting light pollution has been unmatched by most cities and has provided some of the best stargazing from an urbanized area. Even after the frontier ended as Flagstaff became more established, the night sky still remains largely untouched by the city limits. The effort allows many to clearly see the limitless cosmos, the same one that Lowell had seen over a hundred years ago when building his observatory.  


Bartels, Meghan. “Meet the Unknown Female Mathematician Whose Calculations Helped Discover Pluto.” Space.Com, February 18, 2020. 

Douglass, A.E. “Sorry That It Won’t Be Southern Arizona for the Site of the Observatory,” April 16, 1894. 

International Dark-Sky Association. “Flagstaff AZ Images at Night Show Success with Years of Dark Sky Advocacy,” January 20, 2017. 

Gilbert, Sarah. “A Brief History of a Legendary Telescope » Lowell Observatory.” Lowell Observatory, March 23, 2016. 

International Dark-Sky Association. “Light Pollution.” Accessed January 3, 2023. 

Perkowitz, Sidney. “Eight Women Astronomers You Should Know.” JSTOR Daily, January 5, 2022. 

Rabkin, Eric S. Mars: A Tour of the Human Imagination. Westport, Conn, 2005. 

Seed, David. A Companion to Science Fiction. Malden, MA : Blackwell Pub., 2005. 

“The Girl Who Named a Planet,” January 13, 2006. 

The Sky at Night – The Man Who Discovered A Planet. Accessed January 15, 2023. 

Featured image credit: Percival Lowell Observing Venus from the Lowell Observatory in 1914. Public domain. Image accessed via Wikimedia Commons:

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