Finding Pluto at Lowell Observatory
In 1896, construction of the Lowell Observatory in Flagstaff brought astronomy to the Southwest, sparking a science and a passion that still blazes in Arizona. For over 100 years its research has sharpened our understanding of the universe. Today it is the nation’s premier privately owned research observatory and a favorite observing location for the public.
First Observatory in the Southwest
Lowell Observatory founder Percival Lowell was born to a well-to-do family in Massachusetts. A man of means and many interests, he studied math, wrote books, and traveled extensively before dedicating himself to the study of astronomy in the 1890s. He became fascinated by the idea of canals on Mars and sent Andrew E. Douglass, astronomer and naturalist, to scout the best spot to construct an observatory.
A site near Flagstaff, later christened Mars Hill, proved ideal. The town’s elevation of over 7,000 feet minimized atmospheric interference. Clouds rarely appeared during the dark, starry nights. Flagstaff was growing as a site for cattle ranching and logging from its Ponderosa pine forest, but the town was small and the view of the night sky was brilliantly clear. In addition, the transcontinental railroad ran through town, enabling transport of materials to build the observatory. In 1896, the Clark Telescope—then the height of astronomical technology—became the first observatory telescope in the southwest region.
An Expanding Universe and the Big Bang Theory
Many compelling discoveries made at Lowell are associated with one man: astronomer Vesto Slipher. In 1912, soon after joining Lowell's team, he made an observation that shapes our view of the universe today.
At the time, the information on celestial objects was gauged with a spectrograph, an instrument that separates incoming waves into different frequencies so the frequencies can be studied to glean information about the objects sending them. At Lowell, Slipher began using a spectrograph in ways it had never been used before, capturing multiple exposures over a long period of time. These measurements showed a change in the spectral lines of distant galaxies. In fact, the amount of infrared waves appearing in the measurements increased with the length of exposure. With this information, Slipher correctly deduced that galaxies and other celestial objects were moving away from earth—in short, that the universe was expanding. This movement is called a galactic redshift, and it is the basis of the Big Bang Theory. Hubble used Slipher’s observations and his own equations to create a formula for measuring galaxy distances. Known today as Hubble’s Law, this formula relies heavily on Slipher’s work.
Slipher made several additional contributions to astronomy throughout his career. He discovered the Sodium Layer, a layer of non-ionized atoms in the earth’s mesosphere, in 1929, and oversaw the work that led to the discovery of Pluto. He stayed at Lowell for over 40 years, working as director from 1926 until his retirement in 1952.
In 1905, Lowell became convinced of the existence of an undiscovered planet in our solar system. He began an obsessive search for “Planet X.” Night after night, he would take pictures of the sky, comparing them inch by inch using a magnifying glass. But finding a planet is hard work. Even with today’s high powered telescopes, the universe is a dauntingly vast place to play hide and seek. He was not examining the right part of the sky, and his first search yielded no planet. Searches in 1911 and 1913 returned the same disappointing results.
In 1915, Lowell revised his estimation of the planet’s location and successfully photographed it in July. However, the planet was so much dimmer than he predicted it to be that he did not identify it. He died of a stroke four months later, his dream of discovery unrealized.
In 1928, Lowell’s nephew, Roger Lowell Putnam, became the sole trustee after years of legal strife. He upgraded equipment and built the Pluto Discovery Telescope. He also hired astronomer Clyde Tombaugh to lead the hunt for Planet X.
The search began anew in April 1929. Tombaugh detected the new body in November and verified it by February 18,1930, Pluto's official "discovery date." The name Pluto was chosen because this shadowy planet evoked an homage to Pluto, the Roman god of the underworld, and perhaps because it also incorporated the Percival Lowell’s initials. Fifteen years after his death, Lowell’s dream had come true!
Pluto remained a planet from 1930 to 2006, when it was reclassified as a dwarf planet. Today it is the second largest dwarf planet in our solar system.
In 2011, TIME magazine named the Observatory one of "The World's 100 Most Important Places." Today the Lowell Observatory is one of the world’s largest privately operated research observatories and a popular public attraction.
The Mars Hill site, designated a National Historic Landmark in 1965, is open for night sky viewing via private and group tours and hosts educational camps for school-aged children.
Research continues on several dark sky sites nearby. The Discovery Channel Telescope is located on the Mogollon Rim near Happy Jack. The Anderson Mesa, 12 miles southeast of Flagstaff, houses four research telescopes, including the 72-inch (1.8-meter) Perkins Telescope (in partnership with Boston University) and the 42-inch (1.1 meter) John S. Hall Telescope. Lowell is a partner with the United States Naval Observatory and Naval Research Laboratory in the Navy Precision Optical Interferometer (NPOI), also located at that site.
Appropriately, some of the new research on the Mesa echoes Lowell’s roots. The “How to Find a Planet” program, including the Transatlantic Exoplanet Survey, watches for shifts in distant galaxies that may reveal the existence of faraway planets. Researchers study extrasolar planet atmospheres and the formation of new planetary systems. They also study formation and orbits of binary stars in galaxies far, far away. Closer to home, Titan Monitoring Telescope at the Anderson Mesa studies the atmosphere of Saturn’s largest moon, Titan. The observatory also looks for asteroids approaching earth and studies the origin of comets.