Tesis para optar al grado de Magíster en Ciencias, Mención Astronomía / Planetary Sciences are constantly progressing. Current facilities have allowed the discovery of a considerable amount of exoplanets and a more detailed study of protoplanetary disks, which is where planets are thought to form. Among the important tracers of disk evolution is the measurement of physical properties of these protoplanetary disks. This thesis focuses in two main parts; the first one in the diagnostic of gas line emission; while the second explores disks during even earlier stages of planet formation going through outbursts of accretion. In Chapter 2, we describe a line emission diagnostic that allows the measurement of temperature, turbulent broadening and the column density (particle number per unit surface) in protoplanetary disks. We test our line emission diagnostic through detailed analysis on post processed hydrodynamical simulations of a protoplanetary disk with an embedded giant planet. Our diagnostic could potentially allow the detection of kinematical signatures in line emission of planet-disk interactions, such as the Rossby wave (RWI) vortices associated with giant planet formation. We could conclude that our line emission diagnostic measures a kinematical signature in the disk, although very small. When the line emission diagnostic is applied to the hydrodynamical simulations, the measured turbulent velocity shows a small enhancement for optically thick molecular transitions at the location of the vortex. In Chapter 3, we explored an intriguing class of circumstellar objects, FU Orionis objects. FU Ori objects have outbursts with high accretion rates. They could solve the low luminosity problem in the formation of low mass stars. It is believed that low mass stars go through this phenomenon more than one time during their formation. Chapter 3 addresses how accretion outbursts shape the radial structure of the circumstellar disk in V883 Ori, a FU Ori object. With our approach, we measure its temperature and how fast it accretes. We use a self-iterative algorithm that takes the radial profile of a circumstellar source and returns its shape and how much it is accreting, separating optically thin with optically thick regimes. From our analysis of V883 Ori, we find that passive disk heating mechanisms do not reproduce the steep thermal profile of V883 Ori closer to the star than r=30 AU. Thus, we conclude that viscous dissipation provides the supplemental amount of energy necessary to generate the emission profile observed in V883 Ori. / Beca Magíster Nacional CONICYT, Millenium Nucleus "Protoplanetary Disk in Alma Early Science" y por el Departamento de Postgrado y Postítulo de la Vicerrectoría de Asuntos Acádemicos, Universidad de Chile