Calendar

Mar
28
Wed
Colloquium PhD Thesis Defense: Ethan Dederick
Mar 28 @ 3:15 pm – 4:15 pm
Colloquium PhD Thesis Defense: Ethan Dederick @ Science Hall 109

Seismic Inferences of Gas Giant Planets: Excitation & Interiors

Ethan Dederick, NMSU

Seismology has been the premier tool of study for understanding the interior structure of the Earth, the Sun, and even other stars. In this thesis we develop the framework for the first ever seismic inversion of a rapidly rotating gas giant planet. We extensively test this framework to ensure that the inversions are robust and operate within a linear regime. This framework is then applied to Saturn to solve for its interior density and sound speed profiles to better constrain its interior structure. This is done by incorporating observations of its mode frequencies derived from Linblad and Vertical Resonances in Saturn’s C-ring. We find that although the accuracy of the inversions is mitigated by the limited number of observed modes, we find that Saturn’s core density must be at least 8.97 +/- 0.01 g cm^{-3} below r/R_S = 0.3352 and its sound speed must be greater than 54.09 +/- 0.01 km s^{-1} below r/R_S = 0.2237. These new constraints can aid the development of accurate equations of state and thus help determine the composition in Saturn’s core. In addition, we investigate mode excitation and whether the \kappa-Mechanism can excite modes on Jupiter. While we find that the \kappa-Mechanism does not play a role in Jovian mode excitation, we discover a different opacity driven mechanism, The Radiative Suppression Mechanism, that can excite modes in hot giant planets orbiting extremely close to their host stars if they receive a stellar flux greater than 10^9~erg cm^{-2} s^{-1}. Finally, we investigate whether moist convection is responsible for exciting Jovian modes. Mode driving can occur if, on average, one cloud column with a 1-km radius exists per 6423 km^2 or if ~43 storms with 200 columns, each with a radius of 25 km, erupt per day. While this seems unlikely given current observations, moist convection does have enough thermal energy to drive Jovian oscillations, should it be available to them.

Nov
8
Fri
Colloquium: Jacob Vander Vliet (Host: Chris Churchill)
Nov 8 @ 3:15 pm – 4:15 pm
Colloquium: Jacob Vander Vliet (Host: Chris Churchill) @ BX102

Galaxy Evolution in a Computer Box, or “How to turn a PhD on Theoretical Galaxy Evolution into a Scientific Programming Career with NASA”

Jacob Vander Vliet, NASA/SOFIA

I graduated from NMSU in 2017 with a PhD entitled “Observing the Baryon Cycle in Hydrodynamic Cosmological Simulations”.  I am happy to discuss the journey I took from primarily scientific interest in this problem to a primarily programming and computational interest in this problem.  One of the major outcomes of my dissertation was to build pipeline software for analysis of the hydrodynamic simulations using the “quasar absorption line technique from which we study the circumgalactic medium in the simulations in order to learn about the so-called baryon cycle.  Following graduation, I continued on as a “research assistant” at NMSU, and then landed a job with NASA at Stratospheric Observatory for Infrared Astronomy (SOFIA) and a scientific programmer.  I will discuss the type of science done at SOFIA and the virtues and differences of a non-academic position out of graduate school.