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Imaging protoplanetary discs [Kraus 2021]

Imaging the dynamical processes in the inner regions of protoplanetary discs

Supervisor: Professor Stefan Kraus

The discs around young stars provide the stage for planet formation and the dominant fraction of the planet population is believed to form in the very inner regions of these discs, on scales of a few astronomical units. Photometric monitoring observations indicate that highly dynamical processes are taking place in this inner disc environment, but it is unclear whether this variability is caused by the presence of planets that dynamically sculpt the disc or other disc-related phenomena, such as dusty disc winds or gravitational instabilities.

Even the largest telescopes are only able to resolve the outer disc regions, on scales of tens to hundreds of astronomical units. Infrared interferometry offers an elegant way to overcome this resolution barrier by combining the light from separate smaller telescopes. As part of the Exeter-led CHARA/MIRC-X instrumentation project we recently achieved breakthroughs in interferometric imaging of young stars and obtain now routinely 6-telescope images of the innermost astronomical unit of protoplanetary discs.

The aim of this project is to use these unique new capabilities in order to study the time evolution of the inner disc environment. The project is linked to a 150+ night survey at the CHARA and VLTI array and a rich data set of protoplanetary disc observations is already available. At this extremely high angular resolution (0.001 arcsecond, or 1/5,000,000 of a degree), the orbital timescale is just a few months, which allow us to follow the temporal evolution of any disc asymmetries as they orbit around the star. We will combine our CHARA imagery with SPHERE+ALMA imaging to search for shadows cast by the inner disc components onto the outer disc. Modelling these observations will constrain the 3-dimensional orientation & shape of the disc over a wide range of spatial scales.

In this PhD project you will learn about the physics of protoplanetary discs and planet formation and use innovative high-angular resolution imaging techniques. The successful candidate will work within our team of postgraduate students and postdoctoral researchers and interact closely with theory experts for interpreting the observations. The position offers opportunities to conduct observations at observatories in Chile and/or the United States and, depending on the candidate’s interest, to join our partner group at the University of Michigan for 6 months as visiting researcher. From this research we expect new insights on the origin of the variability in young stars, on protoplanetary disc structure, and on the processes that govern planet formation and planet migration near the dust sublimation region.