With over 5,000 exoplanets discovered since the advent of planetary science, understanding protoplanetary disk evolution remains critical. Although existing models have offered insights, the intricacies regarding the disk's structure and the impact of the host star's parameters on planet formation persist. Utilizing FARGO3D, we simulated the evolution of protoplanetary disks. Critical factors like surface density and the disk-to-host star mass ratio were primarily considered in terms of the host star's mass. After introducing necessary parameters into FARGO3D and integrating test particles for simulation, we assessed the protoplanetary disk's planetary formation capability. Our findings indicate that protoplanetary disks can form planets for host star masses below a certain threshold. However, as the host star's mass augments, its potential for planet formation diminishes, with a notable transition zone observed. Our research elucidates why most exoplanet-hosting stars have masses below this threshold, suggesting it's potentially more related to the intrinsic properties of the protoplanetary disk as determined by the host star rather than observational limitations.

When a star is born, a protoplanetary disk made of gas and dust surrounds the star. The 1 disk can show gaps opened by different astrophysical mechanisms. The gap has a wall emitting 2 radiation which contributes to the spectral energy distribution (SED) of the whole system (star, disk 3 and planet) in the IR band. As these new-born stars are far away from us, its difficult to know 4 whether the gap is opened by a forming planet. I have developed RHADaMAnTe, a computational 5 astro code based on the geometry of the wall gap coming from hydrodynamical 3D simulations of 6 protoplanetary disks. With this code it is possible to make models of disks to estimate synthetic SEDs 7 of the wall gap and prove whether the gap was opened by a forming planet. I have implemented this 8 code to the stellar system LkCa 15. I found that a planet of 10 Jupiter masses is capable of opening a 9 gap with a curved wall with height of 12.9AU. However, the synthetic SED does not fit to Spitzer IRS 10 SED (ξ² ∼ 4.5) from 5µm to 35µm. This implies that there is an optically thick region inside the gap.

Low-energy cosmic rays (LECRs) play a crucial role in the formation of planetary systems, and detecting and reconstructing the properties of early LECRs is essential for understanding the mechanisms of planetary system formation. Given that LECRs interact with the surrounding medium to produce nuclear de-excitation line emissions with energy mainly within 0.1–10 MeV, which are unaffected by stellar wind modulation, these gamma-ray emissions can accurately reflect the properties of LECRs. This study introduces an innovative method for using gamma-ray emissions to infer LECR properties. We employed the Parker transport equation to simulate the propagation and spectral evolution of LECRs in a protoplanetary disk and calculated the characteristic gamma-ray emissions resulting from interactions between LECRs and disk material. These gamma-ray emissions encapsulate the spectral information of LECRs, providing a powerful tool to reconstruct the cosmic ray environment at that time. This method, supported by further theoretical developments and observations, will fundamentally enhance our understanding of the impact of CRs on the origin and evolution of planetary systems and address significant scientific questions regarding the cosmic ray environment at the origin of life.