Over the past half century, astronomers have identified on the order of 2000 Very Metal Poor (VMP) stars with [Fe/H] -2.0, and a few hundred Extremely Metal Poor (EMP) stars with [Fe/H] -3.0, primarily from two large objective prism surveys, the HK survey of Beers and collaborators and the Hamburg/ESO Survey of Christlieb and colleagues. High

We review several experiments in ionospheric modification performed at the HAARP facility. Many of these experiments have been done in bistatic configuration with the WAVES receiver on the NASA/WIND satellite, including study of scintillation-like variations in low frequency propagation through the earth's ionosphere and magnetosphere. The

GJ 569Bab is the first brown dwarf binary for which the mass of each component has been derived by solving the astrometric and spectroscopic orbit of the pair, i.e., independently of any theoretical assumption. This allows us to test the predictions of the various evolutionary models available in the literature. Particularly interesting are the

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Esta tesis está enfocada hacia el estudio de la interacción de las estrellas masivas con el medio interestelar ionizado en dos regiones HII galácticas. Se presentan dos estudios bien diferenciados. El primero trata de la comparación de abundancias químicas en la región de formación estelar asociada con la Nebulosa de Orión (M42), obtenidas a partir

The Local Group Census is a narrowband imaging survey aimed at cataloguing the emission-line populations in the galaxies of the Local Group. Data, which were obtained using the Wide Field Camera of the 2.5m Isaac Newton Telescope, are available to the whole astronomical community, resulting in a valuable imaging resource for follow-up spectroscopy