SETI Institute Weekly Colloquium - Upcoming Speakers
Cosmic Microwave Background (CMB) photons are actually sensitive gravimeters. Using the intensity and polarization properties of these primeval photons, we can measure the gravitational field of the last scattering surface, the fictitious shell formed by the universe’s first hydrogen atoms.
The last scattering surface is also a gravitational wave detector; a thin “film” of matter onto which primordial gravitational waves can be “exposed”, allowing us to peer back to the inflationary epoch when these gravitational waves themselves were produced. If inflation produced a gravitational wave background, then these gravitational waves imprint a unique “swirling” pattern called B-mode polarization.
IF B-mode polarization is proven to be primordial it will be strong evidence that inflation occurred. This is the goal of a dozen experiments planned, or currently plying southern hemisphere skies: including two experiments whose results will be discussed: BICEP2 and POLARBEAR, the first experiments to directly detect the CMB’s B-mode polarization.
Current experimental sensitivities are at the tens of nanoKelvin level, unimaginable just a decade ago when the hunt for B-modes began. Dr. Keating will discuss the fundamental science that can be revealed with such precision instrumentation.
When a hot-Jupiter transits its host star and crosses an active region there is a possibility that it will occult a starspot. When this happens a starspot anomaly is usually seen in the resulting transit lightcurve. Generally viewed as a nuisance, the most common approach is to remove the affected data points before performing an analysis to determine the lightcurve properties. However, when a starspot anomaly is found in transit photometry it can allow a wealth of information to be discovered. Apart from determining the physical properties of the starspot (such as position, size and temperature) if a starspot anomaly is found in two sets of transit photometry and is due to the same starspot it is then possible to determine the stellar rotation period at the given latitude of the starspot. It is also possible to measure the sky-projected stellar obliquity of the system which can then begin to shed some light on the primary mechanism of the dynamical evolution of the system.
The Yellowstone Plateau Volcanic Field is characterized by extensive seismicity, episodes of uplift and subsidence, and a hydrothermal system that comprises more than 10,000 thermal features. Some of the recent advances include more refined geophysical images of the magmatic system, characterization of fluid sources and water-rock interactions, quantitative estimates of heat and magmatic volatile fluxes, discovering and quantifying the role of thermophile microorganisms in the geochemical cycle, defining possible links between hydrothermal activity, deformation, and seismicity; quantifying the dynamics of geyser eruptions, and the discovery of extensive hydrothermal activity in Yellowstone Lake.
Saturn's ring system is an astrophysical disk that is neither light-years away nor billions of years in the past. We can visit this disk at close range and observe a number of phenomena that also operate in disks of other kinds. As a result, we see small-scale processes that shape ring texture, connect those processes to the bodies and structures that cause them, and watch closely as the disk changes with time.
We will discuss recent Cassini observations that elucidate disk processes including 1) "self-gravity wakes" and "spiral density waves," both of which were originally proposed for galaxies but are observed with exquisite precision in Saturn's rings, 2) "propeller" features caused by 100-meter to km-sized moonlets embedded in the disk; these are the first objects ever to have their orbits tracked while embedded in a disk, rather than orbiting in free space, and hold the potential of deepening our understanding of planetary migration, and 3) irregular edge shapes in the gaps opened up by larger moons (10 km and more), which may hold clues to angular momentum transport.