A theoretical look at the direct detection of giant planets outside the Solar System

Astronomy is at times a science of unexpected discovery. When it is, and if we are lucky, new intellectual territories emerge to challenge our views of the cosmos. The recent indirect detections using high-precision Doppler spectroscopy of now more than one hundred giant planets orbiting more than one hundred nearby stars is an example of such rare serendipity. What has been learned has shaken our preconceptions, for none of the planetary systems discovered to date is like our own. However, the key to unlocking a planet's chemical, structural, and evolutionary secrets is the direct detection of the planet's light. I review the embryonic theory of the spectra, atmospheres, and light curves of irradiated giant planets and put this theory into the context of the many proposed astronomical campaigns to image them.Comment: pre-editorial, non-copyrighted version of Review Article just published in Nature. 5 figures, one in JPEG forma

A New Algorithm for 2-D Transport for Astrophysical Simulations: I. General Formulation and Tests for the 1-D Spherical Case

We derive new equations using the mixed-frame approach for one- and two-dimensional (axisymmetric) time-dependent radiation transport and the associated couplings with matter. Our formulation is multi-group and multi-angle and includes anisotropic scattering, frequency(energy)-dependent scattering and absorption, complete velocity dependence to order v/c, rotation, and energy redistribution due to inelastic scattering. Hence, the "2D" realization is actually "6 1/2"-dimensional. The effects of radiation viscosity are automatically incorporated. Moreover, we develop Accelerated-Lambda-Iteration, Krylov subspace (GMRES), Discontinuous-Finite-Element, and Feautrier numerical methods for solving the equations and present the results of one-dimensional numerical tests of the new formalism. The virtues of the mixed-frame approach include simple velocity dependence with no velocity derivatives, straight characteristics, simple physical interpretation, and clear generalization to higher dimensions. Our treatment can be used for both photon and neutrino transport, but we focus on neutrino transport and applications to core-collapse supernova theory in the discussions and examples.Comment: 44 pages, 14 figure