In this video, Sara Seager continues her lecture on exoplanet detection techniques. Seager provides a description of the direct imaging technique, its specific requirements and ground-based limitations, and the importance of the concepts of diffraction and spatial resolution. In direct imaging, given a measurement of brightness, planet mass and size must be inferred from a model, often leading to inaccurate size representations - such is the case of Pluto. The technique remains useful nonetheless. Seager then overviews microlensing, an approach of important aesthetic value that requires tracking one-time lecture events and completing intricate mathematical calculations. Despite its complications, it remains the ideal means to find earth-mass planets. Microlensing may eventually cover an important section of the exoplanet occurrence diagram that is alien to other methods. Finally, astrometry is a technique that will be useful in completing the exoplanet discovery spectrum in the future, despite not having any formal planet detections yet. The final goal, Seager concludes, is to complete the occurrence plot as much as possible, and in the process, to discover distinct features that will allow scientists to better understand planet formation.

See: Exoplanet Detection: Techniques I, for the first half of this lecture.