Lowell Observatory

Lowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965. The Observatory's original 24-inch (0.61 m) Alvan Clark Telescope is still in use today for public education. Lowell Observatory hosts 70,000 visitors per year at their Steele Visitors Center who take guided daytime tours and view various wonders of the night sky through the Clark Telescope and other telescopes. It was founded by astronomer Percival Lowell, and run for a time by his third cousin Guy Lowell of Boston's well-known Lowell family. The current trustee of Lowell Observatory is William Lowell Putnam, grandnephew of founder Percival Lowell and son of long-time trustee Roger Putnam. The position of trustee is historically handed down through the family. The observatory operates several telescopes at two locations in Flagstaff. The main facility, located on Mars Hill just west of downtown Flagstaff, houses the original 24-inch (0.61 m) Clark Refracting Telescope, although its role today is as a public education tool and not research. The telescope, built in 1896 for $20,000, was assembled in Boston by Alvan Clark and then shipped by train to Flagstaff. Also located on the Mars Hill campus is the 13-inch (0.33 m) Pluto Discovery Telescope, used by Clyde Tombaugh in 1930 to discover the dwarf planet Pluto. Lowell Observatory currently operates four research telescopes at its Anderson Mesa dark sky site, located 20 km (12 miles) southeast of Flagstaff, including the 72-inch (1.8-meter) Perkins Telescope (in partnership with Boston University) and the 42-inch (1.1 m) John S. Hall Telescope. Lowell is a partner with the United States Naval Observatory and NRL in the Navy Prototype Optical Interferometer (NPOI) also located at that site. The Observatory also operates smaller research telescopes at its historic site on Mars Hill and in Australia and Chile. Lowell Observatory is currently building the 4.2-meter Discovery Channel Telescope in partnership with Discovery Communications, Inc.

The original goal of the observatory was to measure solar irradiance variability. When Harold L. Johnson took over in 1952, the stated objective became to focus on light from the Sun reflecting off of Uranus and Neptune. In 1953, the current 21-inch telescope was installed. Starting in 1954, the telescope began monitoring Uranus' and Neptune's brightness, and matching them against a reference set of sun-like stars.

Discovery Channel Telescope
Lowell Observatory is building a major new telescope in partnership with Discovery Communications near Happy Jack in northern Arizona. The telescope, located within the Mogollon Rim Ranger District of the Coconino National Forest, is expected to be the fifth largest in the continental United States and will allow Lowell astronomers to enter new research areas and conduct existing programs more effectively and efficiently. The DCT and the research it enables also will be the focus of ongoing informative and educational television programs about astronomy, science, and technology airing on Discovery networks. In addition, the Discovery Channel Telescope at Lowell Observatory is expected to have a significant educational and economic impact within the state. The primary mirror, measuring 4.1 meters in diameter and 4 inches thick, is notable for its unique meniscus design for such a large mirror. It is currently being polished at the Optical Fabrication and Engineering Facility at the College of Optical Sciences, University of Arizona. The College of Optical Sciences is one of only a handful of facilities in the world that can handle the difficulty of fabricating this mirror.

Current research
Lowell Observatory's astronomers conduct research on a wide range of solar system and astrophysical topics using ground-based, airborne, and space-based telescopes. Among the many current programs are a search for near-Earth asteroids, a survey of the Kuiper Belt beyond Neptune, a search for extrasolar planets, a decades-long study of the brightness stability of the sun, and a variety of investigations of star formation and other processes in distant galaxies. In addition, the Observatory staff designs and builds custom instrumentation for use on Lowell's telescopes and elsewhere. For example, Lowell staff built a sophisticated high-speed camera for use on the Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is a joint project of the United States and German space agencies and consists of a 2.5-meter telescope on board a Boeing 747 SP.

Notable discoveries
  • The solar system body Pluto by Clyde Tombaugh in 1930.
  • Large recessional velocities of galaxies by Vesto Melvin Slipher between 1912 and 1914 (that led ultimately to the realization our universe is expanding).
  • Co-discovery of the rings of Uranus in 1977.
  • The periodic variation in the activity of Comet Halley during the 1985/1986 apparition.
  • The three largest known stars.
  • The atmosphere of Pluto.
  • Accurate orbits for two of Pluto's moons: Nix and Hydra.
  • Oxygen on Jupiter's satellite Ganymede.
  • Carbon dioxide ice on three Uranian satellites.
  • The first Trojan of Neptune.
  • Evidence that the atmosphere of HD 209458 b contains water vapor.