Caldwell, John

John Caldwell

Full Professor
Retired
Ph.D. (Wisconson)

Department(s): Physics and Astronomy

Office:
Phone: ext.

Research Fields
Astronomy and Astrophysics, Planetary Physics

Research Types
Experimental


Research specialization
Planetary astronomy, especially from space; Planetary atmospheres; Extra-solar planets.


My research is primarily, but not exclusively, related to observations made with the Hubble Space Telescope (HST). Past and continuing research has been concentrated on the atmospheres of planets and satellites. Planetary studies have included atmospheric composition, haze and cloud effects, and aurorae.

Other topics of interest include planetary lightning and the influence of Raman scattering on spectra. Among the planets, the emphasis has been on the gas giants. Of the satellites, Titan has received the most attention, followed by Io. Titan is particularly interesting because its atmosphere is unique among satellites in the solar system, having a column abundance ten times greater than that of planet Earth, and a distinctive composition including numerous hydrocarbon and nitrile molecules. There are also condensate cloud layers and high altitude hazes, the latter probably of photochemical origin. Titan exhibits clear seasonal effects, manifested in hemispheric brightness asymmetries, although the dynamics of the atmosphere have been essentially not observed in detail.

A developing interest is the study of extra-solar planets. Initially, discoveries were made exclusively by using precise, high resolution Doppler spectroscopy to measure the reflex motion of the parent stars due to the small but significant gravitational pull of the planets’ masses. We participate in complementary techniques, including attempts to image planets and other stellar companions directly with the Hubble Space Telescope and to observe planetary transits with the Kepler space observatory.