Dissertation defence (Astronomy): Msc Yasir Abdul Qadir
Msc Yasir Abdul Qadir defends the dissertation in Astronomy titled “Multi-color High-precision Optical Polarimetry of Binary Stars and Exoplanets” at the University of Turku on 5 December 2025 at 12.00. The defence is a remote event.
The audience can participate in the defence by remote access: https://utu.zoom.us/j/63638962431
Opponent: Dr. Vitaly Neustroev (University of Oulu, Finland)
Custos: Professor Juri Poutanen (University of Turku)
Doctoral Dissertation at UTUPub: https://www.utupub.fi/handle/10024/194383
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Summary of the Doctoral Dissertation:
Light carries subtle information about the objects it interacts with. Understanding how starlight is scattered by a binary companion or a planetary atmosphere requires detecting tiny variations in this radiation. One of the most sensitive techniques for measuring such variations is polarimetry, which quantifies changes in the orientation of light caused by scattering in stellar winds or planetary atmospheres.
In my dissertation, I use polarimetric observations from the high-precision DiPol-2 multiband polarimeter, an instrument that measures polarization simultaneously in three bands (B, V, and R). This capability enables detailed studies of both massive binary stars and exoplanet systems.
For hot, early-type binary stars, DiPol-2 reveals clear, orbit-dependent polarization patterns produced as starlight scatters in circumstellar material. By analyzing these patterns, my work constrains key orbital properties—including the inclination, orientation, and mass-loss rates of these systems. In contrast, for exoplanets, the polarized signal is extremely faint, originating from the small fraction of starlight reflected by the planet. My research evaluates the detectability of these weak signals with current instruments and lays the groundwork for future polarimetric observations that could reveal more about exoplanetary atmospheres.
Overall, the dissertation demonstrates that high-precision, multiband polarimetry with DiPol-2 provides a powerful and independent method for probing the geometry and physical environments of both stellar and planetary systems. As instrumentation continues to advance, polarimetry will play an increasingly central role in studying stellar evolution and the diversity of planets beyond our Solar System.
The audience can participate in the defence by remote access: https://utu.zoom.us/j/63638962431
Opponent: Dr. Vitaly Neustroev (University of Oulu, Finland)
Custos: Professor Juri Poutanen (University of Turku)
Doctoral Dissertation at UTUPub: https://www.utupub.fi/handle/10024/194383
***
Summary of the Doctoral Dissertation:
Light carries subtle information about the objects it interacts with. Understanding how starlight is scattered by a binary companion or a planetary atmosphere requires detecting tiny variations in this radiation. One of the most sensitive techniques for measuring such variations is polarimetry, which quantifies changes in the orientation of light caused by scattering in stellar winds or planetary atmospheres.
In my dissertation, I use polarimetric observations from the high-precision DiPol-2 multiband polarimeter, an instrument that measures polarization simultaneously in three bands (B, V, and R). This capability enables detailed studies of both massive binary stars and exoplanet systems.
For hot, early-type binary stars, DiPol-2 reveals clear, orbit-dependent polarization patterns produced as starlight scatters in circumstellar material. By analyzing these patterns, my work constrains key orbital properties—including the inclination, orientation, and mass-loss rates of these systems. In contrast, for exoplanets, the polarized signal is extremely faint, originating from the small fraction of starlight reflected by the planet. My research evaluates the detectability of these weak signals with current instruments and lays the groundwork for future polarimetric observations that could reveal more about exoplanetary atmospheres.
Overall, the dissertation demonstrates that high-precision, multiband polarimetry with DiPol-2 provides a powerful and independent method for probing the geometry and physical environments of both stellar and planetary systems. As instrumentation continues to advance, polarimetry will play an increasingly central role in studying stellar evolution and the diversity of planets beyond our Solar System.
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