Colloquium Archive

Wednesday, September 9th
Physics & Astronomy Department Afternoon Tea

4:00pm
Tome Hall 2nd Floor Lounge Area
Tea & cookies provided

Monday, October 5th
Physics & Astronomy Department Afternoon Tea
Professor Ryan will discuss physics behind our weather

4:00pm
Tome Hall 2nd Floor Lounge Area
Tea & cookies provided 

Thursday, October 29th
Dr. Catrina Hamilton-Drager & Nicole Foley
Evidence of Ices and Possible Planetary Formation Zones in ~2-3 Myr Edge-on T Tauri Binary KH 15D

The study of the evolution of planetary material in young protoplanetary disks elucidates the origins of habitable regions of our Galaxy. In our solar system radio-isotopic analyses of the earliest condensed solids, Calcium Aluminum rich Inclusions (CAIs), measures their formation in the first 0-500 kyr (time 0 then being set as the oldest CAI age). Dynamical constraints estimate that Jupiter-sized gas giants began forming (although not completely) within 1-10 kyr and terrestrial-sized objects formed within 100 kyr. Recent evidence from molybdenum and iron isotopic studies of ancient iron meteorites are indicative of two separate reservoirs from which planets were formed created approximately 1 Myr after the CAIs and remaining separate for up to an additional 3 Myr. Formation of large planets are postulated by the meteorite studies to separate planetary building materials during a heavy bombardment period involving formation, alteration, destruction, and re-distribution of materials within Planetary Formation Zones (PFZs). Examining ~2-3 Myr protoplanetary disks and their distribution of organics, ices, gases, and minerals along the mid-plane enables a direct view of PFZ formation.

Furthering the knowledge of such disk constituents is vital to our understanding of the origins of life and habitable zones. The pioneering work done by the James Webb Space Telescope (JWST) of edge-on protoplanetary systems confirmed detection of major ice species H2O, CO2 and CO with a wide range of optical depths along with traces of ammonium salts, possible NH3 hydrates, possible HCOOH, OCN, OCS, varying PAH emissions, and gas emissions of H2, H2O, and CO. The factor of ~3-6 variations in major ice band depths for different edge-on disks is most likely due to abundance variations but may also be due to sampling of different regions of the disks. Radial measurements of the disk volatiles and other components have been challenging due to geometric constraints.

The circumbinary disk in the ~2-3 Myr KH 15D system is currently oriented such that the stars can be used as probes of the disk material, allowing examination of the volatiles along the mid-plane. This talk will summarize the possible volatile species revealed within the KH 15D system via the spectro-photometric data collected by NASA’s SPHEREx telescope. Combined with the recent ground-based photometry, we discuss the evidence that may support the presence of possible PFZs.

Noon
Tome 115
Pizza provided

Thursday, November 12th
Lydia Spychalla, Graduate Student
Penn State University
"How does a large hailstone grow? Untangling hail growth pathways in severe storms"

Hail is the most damaging severe storm hazard in the United States. Accurate hail prediction and forecasting is important for the protection of life and property and helps prepare communities for potential hail risk. High-quality hail forecasts require a good understanding of the hail growth processes and storm conditions that produce large hail. However, robust hail science is constrained by hail observing limitations. Most hail goes unobserved after falling far from roads and populations centers, and observed hailstones often melt substantially on the ground before being measured. Growing hailstones are practically impossible to observe because of the danger of flying into severe storms. To combat these observational limitations, hail trajectory models have been developed to simulate the growth and fall of hailstones that cannot be reliably observed in the real world. Hail trajectory models have identified multiple unique pathways to large hail growth in supercell storms. These hail growth pathways are explored in a high-resolution storm simulation, and the contribution of three pathways to bulk hail production is analyzed: The classical pathway produces the majority of small hailstones; the anti-cyclonic pathway produces fewer, but larger hailstones; and a two-stage pathway produces extremely rare, but extremely large hailstones. In a second simulation, the giant (D > 10 cm) hail trajectories are explored, revealing the storm features responsible for opening and closing a left-turning hail growth pathway that produces giant hail.

Noon
Tome 115
Lunch provided