This week's PhD colloquia are highlighted.
|Predicting the Future: Predictive Control for Astronomical Adaptive Optics|
Current, high contrast imaging (HCI) systems are able to achieve contrast levels of 10-5.5 (5-sigma) for angular separations greater than 3 lambda/D. At smaller angular separations, the contrast dramatically decreases due to AO residuals. Specifically, when there is fast turbulence above the telescope the AO system becomes dominated by the time-lag error (i.e., the servo-lag error). To minimise the time-lag error, I investigate predictive control which makes use of most recent measurements to predict how the atmospheric turbulence evolves of the time lag. More specifically, I look at the following questions: 1) Are the statistics of atmospheric-induced phase fluctuations time-variant? 2) If so, by how much and how quickly do they vary? 3) How do these variations affect prediction? 4) Can we improve upon this? I will also present work on periodic brightening events seen by the Kepler Mission. I look at eight objects and try to explain the behaviour using two very different physical systems: 1) a heartbeat star and 2) forward scattering of a dust cloud around an exoplanet.
|Maaike Van Kooten||Leiden|
|11:15||Sizing up protoplanetary disks|
Although we are certain that planets can be formed, there are still large gaps in our understanding of how they formed. Observations show that exoplanets are found in a large variety of planetary systems, from multiple terrestial planets packed inside the central ~1 AU to several gas giants spread over tens of AU from the central star. The diverse outcomes of planet formation are intimately linked to the disks of gas and dust around young stars, called protoplanetary disks, in which these planets have formed and grown. How much material do these disks contain for planet formation? Is this material concentrated close to the star or spread over a large area? And how do the gas and dust that make up the disk evolve over time? In my talk I will show how studying bulk properties of protoplanetary disks, especially their size, can answer these questions and help us solve the riddle of planet formation.
|11:15||Novel approaches for direct exoplanet imaging: theory, simulations and experiments|