Free-floating planetary-mass objects (PMOs) in star-forming regions represent the low end of the stellar initial mass function and overlap in mass with the high end of the exoplanet population. As such, they share characteristics with both brown dwarfs and giant planets, and could help advance our understanding of star and planet formation. In particular, for the first time, the James Webb Space Telescope affords the opportunity to search for objects down to the opacity limit for fragmentation. I will present findings from a series of observational studies, spanning from the optical to the mid-infrared using the JWST and the largest ground-based telescopes, that shed light on the prevalence and properties of PMOs. Our ultra-deep spectroscopic survey of the NGC1333 young star cluster identified PMOs down to ~5 Jupiter masses, but the paucity of objects at even lower masses is intriguing. Our search for wide binaries revealed a young brown dwarf with a planetary-mass companion. We found silicate absorption features in the photospheres of two of our targets, the first such detections in very young PMOs, indicating silicate clouds in their cool atmospheres. Other targets showed mid-infrared excess, as well as silicate emission features, demonstrating the presence of dusty disks. We also detected emission lines from hydrocarbon molecules in the disks of several targets as well as evidence of ongoing accretion. Moreover, multi-epoch ground-based spectroscopy of one object revealed dramatic changes in accretion-related emission lines over a timescale of weeks, indicative of an accretion burst –the first time such an event has been seen in a PMO. Our JWST spectroscopy during the burst phase showed clear changes in the molecular lines compared to quiescence, including the appearance of water vapor emission, the first time that chemical changes due to increased accretion are observed in a disk around a substellar object. I will comment on the implications of these findings and preview on-going investigations.
Ray Jayawardhana, President-Elect, Caltech
Host: Fred Rasio
CIERA ASTROPHYSICS
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