Planets Close-in and Far-out

Abstract: The data-rich Kepler mission provided an unprecedented view of the demographics of planetary systems. The bulk compositions of planets inform us the time and the location of their birth. Close-in super-Earths are massive enough to trigger runaway gas accretion, yet they accreted atmospheres that weigh only a few percent of the total mass, keeping their sizes below that of the Neptune. This puzzle is solved if super-Earths formed late, in the inner cavities of transitional disks. Over a wide range of nebular depletion histories, super-Earths can robustly build their ~1% by mass envelopes. Super-puffs present the inverse problem of being too voluminous for their small masses. I will show that super-puffs most easily acquire their thick atmospheres as dust-free, rapidly cooling worlds outside 1 AU, and then migrate in just after super-Earths appear. I will conclude by discussing pathways toward understanding the diversity of exoplanets in preparation for the upcoming and planned space missions and ground-based instruments.