January 31, 2023

Speaker: Dave Stevenson (California Institute of Technology)

Contact Information: djs@gps.caltech.edu

Title: Mixing and Unmixing in Planets

Abstract: Planets are not layered in general. The strong evidence of layering on Earth arises because the main components (mantle and core) are immiscible. This is a thermodynamic property and nothing to do with gravity. However, immiscible phases can macrosegregate, allowing gravity to place the more dense component at the bottom. Diffusion of the higher molecular weight species is slow and frustrated by convection. However, central concentration of heavy elements can arise in giant planets (including ice giants) because of the way planets are assembled: The densest material is also the material that aggregates first, and hydrogen is accreted on top. In this case, the various constituent parts are miscible (unlike the case of mantle and core on Earth) but separated at birth. In sufficiently massive "SuperEarths", there should be no core and mantle because entropy wins. I will discuss our current understanding of the imperfect separation of core from mantle on Earth and the extent to which a compositional gradient in giant planets may be legacy of formation.

Visitor's room: Room 111A

Visit Schedule:

Tuesday (31 Jan. 2023):

  • 9:30 a.m.: Jeremy Goodman (Peyton 129)

  • 10:00 a.m: Gaspar Bakos (Peyton 133)

  • 10:30 a.m.: Coffee and informal chat

  • 11:00 a.m.: Colloquium

  • 11:30 a.m.: Colloquium

  • 12:00 p.m.: Bahcall lunch

  • 12:30 p.m.: Bahcall lunch

  • 1:00 p.m.: Bahcall lunch

  • 1:30 p.m.: Josh Winn (Peyton 125)

  • 2:00 p.m.: Tea time with Grad Students (Grand Central)

  • 2:30 p.m.: Tea time with Grad Students (Grand Central)

  • 3:00 p.m.: Bruce Draine (Peyton 108)

  • 3:30 p.m.: Nicole Shibley (Visitor's Room)

  • 4:00 p.m.: Robert Lupton (Peyton 25; in the basement, near the loading dock)

  • 4:30 p.m.: Adam Burrows (Peyton 105)

  • 5:00 p.m.: Eliot Quataert (Peyton 127)


Dinner Sign-up - add your name here:

Tuesday (31 Jan. 2023)

  1. Faculty Host: Robert Lupton

  2. Postdoc Host: Ankan Sur

  3. Jiaxuan Li

  4. Yilun Ma

  5. Josh Winn

  6. He Jia

  7. Rob Tejada

  8. Nicole Shibley

STUDENTS HAVE PRIORITY.

PLEASE NO MORE THAN 8 PEOPLE (it is more difficult to properly interact with the speaker in larger groups).