Dr. Joel Green, University of Texas at Austin
Infrared spectroscopy of newly forming star and planetary systems in molecular clouds in our neighborhood provides a window into the formation of our solar system. Protostars represent a key phase in that star formation history -- after the collapse of a single core within a molecular cloud, tracing the assembly of the key materials (gas, ice, and dust) available for planet formation as the system contracts and irradiates its contents, prior to the complete unveiling of the system with the dispersal of the remaining envelope, perhaps in violent outburst. The Herschel Space Observatory used its infrared eyes to view systems still cloaked in their envelopes and surrounding cloud, probing key diagnostics - in particular, rotational and rovibrational emission lines of CO, OH, and water vapor, forbidden atomic/ionic emission lines, as well as dust emission. Our Herschel programs probe a diverse sample of nearby protostars, to answer the key question: what mechanism controls the material available at the time of planet formation? In particular, we highlight results from rare episodic eruptors with dramatically raised accretion rates, known as "FU Orionis objects", demonstrating that the formation of a star and planetary system is not a smooth process but a slow trickle punctuated by violent floods of activity.