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