RAPTOR · Revealing Accreting Planets Through Observations and Refined simulations

Recent multi-wavelength observations disclosed a groundbreaking discovery—an accreting giant planet surrounded by a circumplanetary disk within the gap of the young circumstellar disk PDS 70. We now witnessplanet formation, one of the forefront themes in modern astrophysics, in action. With over 5,000 detected planetary systems, we have learned that nearly every star in our galaxy hosts at least one planet. The crucial insightinto how these planets form lies in the conjunction of theoretical studies and observations of magnetized dustyaccretion disks - rotating masses of gas and dust around freshly formed stars.Global magneto-hydrodynamical disk models reveal gas evolution, characterizing the accumulation of sub-micron grains and concentration of pebbles. Models with embedded planets and improved thermodynamicsshowcase the gap and ring structure formation. However, modeling both becomes essential when focusing on the scales of young planets. Which physical process determines the mass budget the planets can accrete? Manyobserved exoplanetary systems, such as TRAPPIST-1, show a distinct mass limit of several Earth masses. Whatprevents dust pebbles from further accreting onto these super-Earths? What is the role of the envelope and circumplanetary disk for giant planets’ gas and solid material content?Addressing these crucial questions requires a new class of models that incorporate (1) adaptive mesh refinement for mass tracking near the planet, (2) modeling of magnetic fields from circumplanetary disk scales to theplanet, and (3) radiative transfer for comprehensive heating and cooling across all scales, unveiling the envelopeand circumplanetary disk formation. The astonishing discoveries underline that the next generation of theoretical models is needed. The RAPTOR project goes beyond explaining the observed structures of planet-formingdisks. It will unveil how gas and dust materials build up the planets in detail never reached before.