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The Late-Time Formation and Dynamical Signatures of Small Planets

Eve Lee (Berkeley) — November 3, 2016

Abstract

The Kepler mission has established that approximately half of all Sun-like stars harbor planets. Of these, close-in super-Earths are the most common. Understanding the origin of super-Earths can lend us insight into the default pathway of planet formation. The riddle posed by super-Earths is that they are not Jupiters: their core masses are large enough to trigger runaway gas accretion, yet somehow super-Earths accreted atmospheres that weigh only a few percent of their total mass. I will show that this puzzle is solved if super- Earths formed late, in the inner cavities of transitional disks. 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. Small planets may remain ubiquitous out to large orbital distances. I will demonstrate that the variety of debris disk morphologies revealed by scattered light images can be explained by viewing an eccentric disk, secularly forced by a planet of just a few Earth masses, from different observing angles. The farthest reaches of planetary systems may be perturbed by eccentric super-Earths.