Seminars

Observing a Star:  Our Changing Sun

Dr. J. Todd Hoeksema, Senior Research Scientist W. H. Hansen Experimental Physics Lab, Stanford University
Friday, September 29, SB110

Thankfully the Sun is a reliable and steady source of energy, but when observed carefully, variability on time scales of milliseconds to millennia reveals much about our nearest star. The more familiar photosphere, where dark sunspots appear on an irregular 11-year cycle, is very photogenic, but how can images be turned into measurements? Sound waves detectable at the solar surface penetrate the interior and reveal physical conditions far below. Space-based ultraviolet instruments measure the dynamic high-temperature solar atmosphere. Special telescopes sensitive to polarized light sense the magnetic field, where energy stored above active regions causes flares and coronal mass ejections. How predictable is this space weather that can create hazardous conditions for life and society here on Earth? Todd Hoeksema, recipient of Calvin University’s Distinguished Alumni Award in 2017, will present some of the latest discoveries about our sun and the instruments designed to study it.

Dr. Erik Meijles, Physical Geographer and Lecturer at the University of Groningen, the Netherlands
Tuesday, September 26, 3:30 PM, Commons Lecture Hall

In recent years, earthquakes have started to develop in Groningen, The Netherlands. Although the area has experienced substantial but steady land subsidence due to natural gas extraction for decades, the tremors are a new phenomenon. The infamous Huizinga tremor in 2012 has triggered widespread concern, mainly focusing on property damage, safety issues, house price reduction and psychological problems in an area that never experienced earthquakes before. For several reasons, stopping or even reducing gas production appears to be difficult causing social unrest. In this lecture, I will detail the full extent of the problems and I will relate them to deep and shallow subsurface geology of the region, including recent research developments.

Dr. Jason Smolinski and student Alex VanKooten, Calvin University
Tuesday, October 10, 3:30 PM, SB110

Distinguishing Stellar Populations in Globular Star Clusters: Procedure Validation

Once thought to host a single stellar population, nearly all globular star clusters are now believed to harbor multiple stellar populations, distinguishable most often by multiple sequences on the red giant branch (RGB) of a color-magnitude diagram. The nature of these subgroups can provide insight into the formation history of globular clusters and how they have contributed to the growth of the Milky Way. Such distinct sequences of stars are not often visible to the eye on these diagrams, but with sufficiently precise photometry they can be distinguished statistically. In this talk we present a validation of our procedure to distinguish multiple populations using ground-based data from the Calvin-Rehoboth Observatory for the globular cluster Messier 13 and the evolved open cluster NGC 6791. Results for both clusters agree well with published observations, giving us confidence that we can obtain data of sufficient quality and implement a procedure of sufficient precision to distinguish these stellar populations.

Dr. Joshua Veazey, Grand Valley State University
Tuesday, November 28, 3:30 PM, SB110

Sketching with Nano Probes:  Device creation at oxide interfaces and in multiferroics

The peculiar behaviors of electrons confined to very tiny, nanoscale structures is an active frontier in condensed matter physics today. Fabrication of the structures required to study these physics often involves long, multistep material growth and removal algorithms, presenting barriers involving time and cost. An alternative and relatively new approach that may be appropriate for many oxide materials is direct-writing (or ‘sketching’) of nanostructures using an atomic force microscope (AFM) that sits on a table top. In this talk, I will discuss research into the exotic physics accessible by this technique in the context of two material systems: oxide interfaces and thin-film multiferroics grown on silicon.