Pluto has been a target of research in Flagstaff and at Lowell Observatory since Percival Lowell began his search in 1905.

As of March 13, 1930, the newly-announced planet found itself in need of a name. In a Lowell Observatory Circular dated May 1, 1930, the Observatory designated Pluto as the name for the new planet, based on the suggestion of 11-year-old Venetia Burney of England. In the circular, written by V.M. Slipher, a symbol for Pluto is also suggested, combining its first two letters, P and L, which are also Percival Lowell’s initials. The symbol was later modified slightly.


Charon appears as an elongated part of Pluto in the discovery image (at left). James Christy noticed Pluto’s shape appeared to change from image to image, and deduced Charon’s existence.

In 1978, James Christy of the US Naval Observatory Flagstaff Station (NOFS) discovered Pluto’s largest moon and named it Charon. See Christy’s paper about the discovery, “The Satellite of Pluto,” here .

In 1988, Pluto’s atmosphere was co-discovered by two teams of astronomers that included former Lowell Director Robert Millis, astronomer Larry Wassermann, along with other scientists with later Lowell ties – Ted Dunham, Jim Elliot and Amanda Bosh.  Here is the paper they wrote about the discovery .  Additionally, the first occultation done with NASA’s airborne observatory, SOFIA, was of Pluto, and was made by Ted Dunham, Stephen Levine, and Amanda Bosh, using an instrument built at Lowell for the SOFIA telescope.

In 2005, Pluto’s moons Nix and Hydra were discovered by a team of scientists including former Lowell astronomers Marc Buie and John Spencer.

Today, Lowell astronomers Will Grundy and Henry Roe study the compositions and evolution of solid surfaces of solar system objects by means of visible and infrared telescope observations, laboratory studies, and theoretical models.  Will is particularly interested in the icy surfaces of outer solar system objects including Pluto, Eris, and Makemake, the icy satellites of giant planets, centaurs, and Kuiper belt objects. Among these objects, a large fraction are binaries or multiple systems, which makes it possible to determine their masses and thus densities, which Will has been doing by means of high spatial resolution imaging from the Hubble, Keck, and Gemini telescopes.

The largest of these icy worlds feature surface compositions including materials we normally think of as liquids and gases like water, oxygen, nitrogen, methane, carbon monoxide, and carbon dioxide, all frozen solid by the extremely cold temperatures prevalent in the outer solar system. These exotic solids are sculpted by a rich array of chemical and physical processes, including sunlight-powered sublimation, leading to geysers and other bizarre landforms, as well as complex chemical reactions driven by the harsh radiation of space (from which we are fortunate to be mostly protected by Earth’s atmosphere).

To improve our understanding of these phenomena, Will Grundy collaborates today with Northern Arizona University astronomers Stephen Tegler, Randy Dillingham, and David Trilling to grow methane-nitrogen ice mixtures in an environment that simulates the cold and near vacuum of space on Pluto’s surface.

Will and others in Flagstaff are now contributing to our greatest Pluto adventure yet – the New Horizons mission to Pluto and the Kuiper Belt.

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