Studying Planet Formation with Extreme Angular Resolution from the Ground and Space

Direct imaging is a powerful tool for exploring exoplanet atmospheres and is able to shed light on fundamental questions of formation, composition and habitability. For studies of young self-luminous Jovian planets contrast requirements are loosened and instead angular resolution becomes the limiting factor. For example, translating orbital separations of ~3-5 AU (where we expect such planets to be abundant) to angular resolutions results in values of ~50-100 milliarcseconds at distances to nearby star forming regions. This is well below inner working angles where conventional imaging is sensitive. Discovering young Jovian planets and in particular those which are actively accreting is key to answering many open questions in planet formation. Within this context I will present results from a program to develop a robust kernel phase interferometry (KPI) pipeline for the CHARIS/SCExAO instrument on Subaru and for JWST/NIRSpec. KPI is a proven but underutilized interferometric data processing method which allows us to search for bright exoplanets and protoplanets down to λ/2D. This more than doubles the typical angular resolution sensitivity of a direct imaging planet search. By utilising KPI in this way it is possible to search for Jovian mass planets at orbital separations down to as low as 4 AU for nearby young stars in Taurus.This covers a region of the parameter space which is the target of future upgraded direct imaging experiments such as SPHERE+ and GPI2.0. However, with KPI and CHARIS/SCExAO, we are able to discover new planets at these orbital separations today. I have demonstrated that this technique works with CHARIS/SCExAO, and have applied it to several young stars with known planet candidates including one which we are actively following-up. Finally I will present results from the development of a KPI pipeline for the JWST NIRSpec instrument. This has the potential to unlock a high-angular resolution spectroscopy mode for the JWST, which could enable the characterisation of young exoplanets down to orbital periods of a ~4-5 AU. This work is complementary to on-going efforts by other members of the community to develop KPI for JWST/NIRCAM and JWST/NIRISS as well as the NIRISS aperture masking interferometry (AMI) mode. Fourier-based methods such as AMI and KPI are powerful techniques for exploring high-angular resolution science and have the potential to significantly contribute to our understanding of exoplanets and planet formation.