Calendar

Nov
9
Mon
Pizza Lunch: Karen Kinemuchi
Nov 9 @ 12:30 pm – 1:30 pm
Pizza Lunch: Karen Kinemuchi

High-precision studies of RR Lyrae Stars

Feb
29
Mon
Pizza Lunch: James McAteer
Feb 29 @ 12:30 pm – 1:30 pm
Pizza Lunch: James McAteer @ AY 119

In Life, 2 things are inevitable

 

Nov
11
Fri
Colloquium: Amy Simon (Host: Nancy Chanover)
Nov 11 @ 3:15 pm – 4:15 pm
Colloquium: Amy Simon (Host: Nancy Chanover) @ Biology Annex 102

Outer Planets Update

Dr. Amy Simon, NASA

The Hubble Outer Planet Atmospheres Legacy (OPAL) program is a yearly program for observing each of the outer planets over two full rotations. Observations began with Uranus in 2014, adding Neptune and Jupiter in 2015 (Saturn will be included in 2018, after the end of the Cassini mission). These observations have provided interesting new discoveries in their own right, but are also now being combined with observations from a number of facilities, including NASA’s IRTF, Keck, the VLA, as well as the Kepler and Spitzer missions to further expand the breadth of science they contain.  This talk will cover the latest observations for each of these planets and what we are learning from these data sets.

 

Apr
7
Fri
Colloquium: Lauren Waszek (Host: Jason Jackiewicz)
Apr 7 @ 3:15 pm – 4:15 pm
Colloquium: Lauren Waszek (Host: Jason Jackiewicz) @ BX102

The growth of Earth’s inner core: a new technique to constrain seismic properties in its outermost layers

Dr. Lauren Waszek, Department of Physics, NMSU

The inner core displays a hemispherical difference in seismic velocity, attenuation, and anisotropy, which is well-established from seismic studies. Recent observations reveal increasingly complex and regional features. However, geodynamical models generally only attempt to explain the basic east-west asymmetry. Regional seismic features, such as depth-dependence anisotropy or variation in hemisphere boundaries, are difficult to reproduce and relatively poorly constrained by seismic data. Processes to generate these complex features are debated.

The structures of the inner core are suggested to be formed as the inner core grows over time. Thus, the most recently-formed outermost layers likely hold the key to understanding the geodynamical mechanisms generating the inner core properties. Current datasets of the uppermost inner core and inner core boundary are limited by uneven data coverage, however. In the very uppermost inner core, seismic waves arrive with similar travel times and interfere, making measurements difficult.

Despite the uneven coverage of current datasets, we can use them to infer a very slow inner core super-rotation. The first ever global tomographical inversion for the inner core allows us to make regional observations, and map the lateral variation in the hemispherical structures. In the uppermost inner core, we have developed a new waveform modeling technique with synthetic data to separate these seismic phases, allowing us to measure the seismic properties in the very uppermost inner core. This, in combination with geodynamical modeling, will help us determine how the inner core hemispheres and other features are generated.

 

 

 

 

 

 

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.