Patrick Harrington does both calculations and observations (HST) of planetary nebulae to understand exactly how the star expels the material which forms the surrounding nebula. Particular interests have been construction of photoionization models, radiative transfer problems, dust and thermal infrared emission in planetary nebulae.

A computer model of the Eskimo Nebula bubble produced by the fast wind from the central star. The model also features an equatorial disk of material. We believe this is similar to the three-dimensional shape of the Eskimo, if we could view it from another angle. From the earth, we are actually looking down the long axis of the bubble. (From Pat Harrington's web page).