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.

Apr
6
Fri
Colloquium PhD Thesis Defense: Sten Hasselquist
Apr 6 @ 3:15 pm – 4:15 pm
Colloquium PhD Thesis Defense: Sten Hasselquist @ BX102

Colloquium Title

Sten Hasselquist, NMSU

Abstract

Apr
20
Fri
Observatory Open House
Apr 20 @ 9:00 pm – 10:00 pm
Observatory Open House

Your hosts for the April Campus Observatory Open House are Jason Jackiewicz, Kathryn Steakley, and Laurel Farris.

May
11
Fri
Observatory Open House
May 11 @ 9:00 pm – 10:00 pm
Observatory Open House

Your hosts for the May Campus Observatory Open House are Nancy Chanover, Trevor Picard, and Drew Chojnowski.

Sep
12
Wed
Colloquium PhD Thesis Defense: Alexander Thelen (Host: Nancy Chanover)
Sep 12 @ 3:00 pm – 4:00 pm
Colloquium PhD Thesis Defense: Alexander Thelen (Host: Nancy Chanover) @ Domenici Hall Room 102

The Chemical Composition and Dynamics of Titan’s Atmosphere as Revealed by ALMA

Alexander Thelen, NMSU

Over the last century, remarkable advances in our understanding of Titan’s atmosphere have been accomplished by a campaign of ground- and space-based observations revealing a wealth of complex, organic species in the moon’s upper atmosphere. Many of Titan’s atmospheric constituents produced through the photochemistry and ionospheric interactions of N2 and CH4 exhibit significant variations with latitude and time, particularly towards the poles and within the winter circumpolar vortex. The measurement of spatial and temporal variations in Titan’s atmosphere enables us to elucidate connections between its dynamics, photochemistry, and the influence of seasonal changes. At the end of the Cassini mission in 2017, we can employ the Atacama Large Millimeter/submillimeter Array (ALMA) for future observations of Titan’s atmosphere. Here we detail the analysis of numerous short integration (~3 minute) ALMA observations from 2012 to 2015 to investigate Titan’s stratospheric composition, temporal variations, and search for new molecular species. Using the Non-linear optimal Estimator for MultivariatE spectral analySIS (NEMESIS) radiative transfer code, we retrieved vertical profiles of temperature and abundance in Titan’s lower stratosphere through mesosphere (~50–550 km) from three spatially independent regions. We modeled CO emission lines to obtain temperature measurements, and retrieved abundance profiles for HCN, HC3N, C3H4, and CH3CN. The combination of integrated flux maps and vertical atmospheric profiles from spatially resolved observations allowed us to study the circulation of Titan’s middle atmosphere during northern spring. We observed increased temperatures in Titan’s stratopause at high northern latitudes and a persistent northern enrichment of HCN, C3H4, and CH3CN during this epoch; however, increased abundances of all molecules in the southern mesosphere, particularly HCN, and spatial maps of HC3N also show evidence for subsidence at the south pole. We validated these measurements through direct comparisons with contemporaneous Cassini data, previous ground-based observations, and photochemical model results. While no new trace species were detected, ALMA has proven to be a highly capable asset to enhance the data from the final few years of the Cassini mission, and for the continued study of Titan’s atmospheric dynamics, composition, and chemistry into Titan’s northern summer.

Sep
14
Fri
Observatory Open House
Sep 14 @ 8:00 pm – 9:00 pm
Observatory Open House @ Tombaugh Observatory

Host: Chris Churchill. Assisted by Trevor Picard, Lauren Kahre, and Ali Hyder

Oct
19
Fri
Observatory Open House
Oct 19 @ 8:00 pm – 9:00 pm
Observatory Open House

Host: James McAteer. Assisted by Laurel Farris, Kristen Luchsinger, and Matthew Varakian

Nov
16
Fri
Observatory Open House
Nov 16 @ 7:00 pm – 8:00 pm
Observatory Open House

Host: Moire Prescott. Assisted by Emma Dahl, Drew Chojnowski, and Oana Vesa.

Dec
7
Fri
Observatory Open House
Dec 7 @ 7:00 pm – 8:00 pm
Observatory Open House

Host: Jason Jackiewicz. Assisted by Jeremy Emmett, Caitlin Doughty, and Annie Hedlund.

Jan
20
Sun
Lunar Eclipse – Public Outreach Event
Jan 20 @ 7:45 pm – 10:30 pm
Lunar Eclipse - Public Outreach Event

The NMSU Astronomy Department will be holding a two-part public event for the January 20th total lunar eclipse!

Starting at 7:45 PM, Professor Kristian Finlator will give a talk on the eclipse in the Biology Annex (located here) from 7:45 PM to 8:15 PM, with a second provisional talk planned at 8:30 PM in case attendance is too high for everyone to fit into the room for the first talk.

From 8:30 pm to 10:30 PM the telescopes at Tombaugh Observatory (located here, a short walk/drive from the Biology Annex) will be opened and graduate students will be on hand to answer questions and run the telescopes. Feel free to come to one or both of these events, or to arrive to the telescopes at any time between 8:30 and 10:30. Please keep in mind, the eclipse begins around 8:30, but totality (or, when the moon turns red from fully entering Earth’s shadow) doesn’t begin until ~9:40 PM. The Society of Astronomy Students will also be on site with hot chocolate!

Parking is available at both locations. If there is a possibility of inclement weather, please call the Observatory Hotline (575-646-6278) to make sure that we will have the telescopes open (if there’s a chance of rain, we will not open the telescopes, and we will leave a message at this number saying so).