Planet formation is a complex process that takes place in the discs around young stars. The dominant fraction of the planet population is believed to form in the inner few astronomical units of these discs. Therefore, it is essential to study the physical processes that take place in these inner disc regions to unveil the initial conditions of planet formation. Studying protoplanetary disc structure and evolution also advances our understanding of how Earth formed and how it developed the conditions for harboring life, addressing one of the oldest questions of humankind. Detailed imaging is also the key for detecting planets that are currently in the process of formation and that could be detectable either through the emission from circumplanetary accretion processes, or through the gravitational influence that these planets exert on the disc.
Observational studies of planet formation in protoplanetary discs are primarily limited by the achieved angular resolution that is set by the telescope diameter. Accordingly, most studies of protoplanetary discs could only investigate 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 coherently combining the light from separate smaller telescopes that can be spread over hundreds of metres, thereby providing the first direct view into the innermost astronomical unit of protoplanetary discs. The key requirement for obtaining direct images with infrared interferometers is the number of telescopes that are combined, which has so far been limited to 4 telescopes for protoplanetary disc observations. The primary objective of the ERC Starting Grant is to push this barrier by equipping the MIRC beam combiner at the CHARA telescope array with an innovative ultra-low read-noise detector system that will permit us to obtain first 6-telescope interferometric observations of low- and intermediate-mass young stars. Increasing from 4 telescopes to 6 telescopes provides 3.5-times more observables per measurements, while the CHARA array offers us 2.5-times longer baselines than what was achieved in earlier observations. This enables us to obtain an image in a single night of observing and to study also the time evolution of any resolved structures.
We use interferometric observations to search for possibly planet-induced structures in the inner regions of protoplanetary discs. We combine interferometric data obtained over a wide wavelength range in order to characterise the resolved structures. Finally, we use interferometric observations in spectral lines to separate accretion onto the star and on putative planets.
