The abundances of oxygen and iron in metal-poor stars have been determined through non-LTE radiative transfer simulations in three-dimensional (3D) hydrodynamical models of their atmospheres. The performing of this type of calculations required to develop first very efficient numerical methods and computer programs. Taking into account that the atmospheres of the stars are 3D systems and the impact of non-LTE effects leads to very significant changes in the derived chemical abundances. It has been concluded that the metalicity of some metal-poor stars could be significantly larger than

Using a gravitational lens, the first precise determination of the extinction curve from the optical to the far UV has been carried out in a galaxy outside the Local Group (a z=0,83). It has turned out to be approximately the same as that observed at the LMC and different from that of our galaxy. These studies reveal the properties of interstellar dust in distant galaxies (Mediavilla et al., 2005, ApJ 619, 749).

Chemical abundances have been measured of PNe and HII regions in Sex A and Sex B, two galaxies located on the outskirts of the Local Group. These PNe are the farthest ones where such a direct abundance measurement has been obtained. PNe and HII regions in Sex B show unexpectedly similar abundances, suggesting a very low chemical enrichment. In Sex A there is only one PN known, and its anomalous chemistry is helping us to develop new models of stellar evolution in very low metallicity environments. Furthermore, new candidate PNe in NGC 6822 have been discovered, increasing the number of

A study comparing the oxygen abundance of stars with planets to stars without planets has been completed. By looking at various indicators of the O abundance, it was discovered that stars with planets generally present higher oxygen abundances. These studies are part of an IAC programme to determine whether significant differences exist between the chemical compositions of stars with and without planets (Ecuvillon, Israelian et al., 2006, A&A 445, 633).

Work by C. Gallart, M. Zoccali y A. Aparicio has been published in the Annual Review of Astronomy and Astrophysics. The article reviews current knowledge about star populations in nearby galaxies, which allow us to study the galaxies' history and evolution (Gallart, Zoccali and Aparicio, 2005, ARAA 43, 387). ARAA volumes are published yearly, by invitation, and have a wide circulation within the astronomy community.

An anomalous emission has been detected in the microwave region of the Perseus Molecular Cloud. This work extends the frequency range of the studies being carried out by the WMAP satellite and finds between 11 and 17 Ghz per emission, 10 times greater than can be explained by normal emission processes in the Milky Way. One possible and attractive explanation is the presence of fullerenes, the bipolar electric emission of which is compatible with the observations (Watson, Rebolo et al., 2005, ApJ 624, L28).