En esta tesis presentamos un estudio morfológico, fotométrico y espectroscópico detallado de una muestra de 20 galaxias Wolf-Rayet (WR). Las galaxias WR son un subtipo de las galaxias H II cuyo espectro integrado muestra líneas de emisión propias de estrellas WR, indicando la presencia de una población importante de estrellas masivas y la juventud

The atmosphere of the Sun is being stirred and reshaped continuously through the emergence of magnetized plasma from the convection zone. Magnetic elements coming from the solar interior produce structures in the photosphere, chromosphere and corona in a bewildering range of length and time scales, from the smallest magnetic tubes to the largest

To model the emergence of magnetic fields at the photosphere, we carried out 3D magneto-hydrodynamics (MHD) simulations using the MURaM code. Our simulations take into account the effects of compressibility, energy exchange via radiative transfer and partial ionization in the equation of state. All these physical ingredients are essential for a

The radiative transfer equation (RTE) gives us information about how the light streams through the medium. It must be inverted in order to obtain the properties of the medium that generated the observation. While there are a number of well discussed methods to approach the solution of the inversion, none of them is suitable for the real-time

LIRIS is a near-infrared (1-2.5 microns) intermediate resolution spectrograph (R=1000-3000) with added capabilities for multi-slit, imaging, coronography, and polarimetry, built by the IAC as a common instrument for the 4.2m WHT (La Palma, Spain). LIRIS has been used as a visiting astronomer instrument at the WHT since summer 2004. The image

We give an overview over the different techniques to detect planets in other stars. A special emphasis is given to the transit method and the French/European CoRoT project, which will be the first space mission with a major dedication to the study the extrasolar planets.