Peale Lecture - Tuesday, October 16, 2018: Satellite Formation

Event Date: 

Tuesday, October 16, 2018 - 3:45pm

Event Date Details: 

2018 Peale Lecture.

Refreshments served at 3:30pm.

Event Location: 

  • Broida 1640
  • Peale Lecture 2018

One of Stan Peale’s research interests was the formation and dynamical evolution of planetary satellites.  I will discuss the formation of the regular satellites in our solar system, thought to have originated by two primary processes:  giant impacts and co-accretion.  The origin of moons by collisions into solid planets is reasonably well-understood. Depending primarily on the impact angle and the mass of the impactor compared to the target, collisions can produce a broad range of satellite-to-planet mass ratios, Msat/Mp, ranging from tiny moons like Mars’ Phobos and Deimos to relatively massive satellites such as the Moon (Msat/Mp = 0.01) and Pluto’s Charon (Msat/Mp = 0.12).   In contrast, the satellite systems of the gas planets in our solar system all have Msat/Mp ~ 10^{-4}.  This similarity is striking given what were presumably different accretion histories for each of these planets.   I will discuss how a common satellite system mass ratio can result when satellites co-accrete within disks produced by gas and solids inflowing to the planet, with a predicted value of (Msat/Mp) ~ 10^{-4} depending rather weakly on disk and inflow parameters. Ultimately, all models of satellite origin must be reconciled with the expected subsequent evolution of satellite orbits due to tidal interaction with the host planet and mutual interactions, an area in which Stan made fundamental contributions.