This paper will be a short review of the topics covered at this conference on “Radiation Hydrodynamics in Stars and Compact Objects.” Rather than attempt to cover all the talks and posters, I will describe what I saw as the main themes and then summarize selected topics that provided unsolved questions. Finally, I will try to decide whether we strayed too far from the original purpose of the meeting. Or, put as a question: Does Radiation Hydrodynamics play a major role in solving a wide range of astrophysical problems?
As described in Mihalas’ introductory talk, radiation can affect an astrophysical plasma, flow, or object in several fashions. First, it can influence the kinematics through ionization, dissociation, and other gas-phase processes that depend on chemistry, ionization state, or excitation. But second, it can influence the dynamics of the flow, through deposition of momentum. Examples of the latter are shock waves, accretion disks, novae, supernovae, and hot-star winds. One can, therefore, divide the topics at this meeting into “active” and “passive” classes of radiation hydrodynamic problems (Table 1). The term “active” implies dynamic pressure from the radiation, whereas the term “passive” allows the radiation to affect the state of the gas, particularly its spectral emissivity, without affecting its motion appreciably.