Un equipo internacional de astrónomos, liderado por Tariq Shahbaz, del Instituto de Astrofísica de Canarias (IAC), y que incluye al también investigador del IAC Jorge Casares, ha descubierto lo que podría ser o bien la primera estrella de neutrones “masiva” o bien el primer agujero negro “de poca masa” observado. Este exótico descubrimiento podría ser el primer indicio de lo masivo que puede llegar a ser un objeto antes de curvarse sobre sí mismo en el espacio para convertirse en un agujero negro. La vida de las estrellas es similar a la nuestra – nacen, envejecen y, finalmente, mueren. La

The galactic gradient of C has been determined for the first time using recombination lines in HII regions. Results from these lines are more reliable than those derived from the traditional collisional excitation lines, which are stronger but subject to variations of temperature in nebulae (Esteban et al., 2005, ApJ 618, 195). These results have made it possible to greatly limit the number of possible models for chemical evolution in the Milky Way.

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).