Transit-radius contribution of a gaseous envelope
= Transit-radius contribution of a gaseous envelope
A low-<mean molecular weight> hydrogen-helium envelope can add a large <radius> while adding a small fraction of the <mass>. The <exoplanet transit photometry> radius is the altitude where tangential <optical depth> becomes order unity, so <temperature>, <opacity>, and <exoplanet clouds> can move the measured radius above the deep material radius. Atmospheric loss and cooling change this contribution over time.