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).
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H II regions are ionized nebulae associated with the formation of massive stars. They exhibit a wealth of emission lines in their spectra that form the basis for estimation of chemical composition. The amount of heavy chemical elements is essential to the understanding of important phenomena such as nucleosynthesis, star formation and chemical evolution of galaxies. For over 80 years, however, a discrepancy exists of a factor of around two between heavy-element abundances (the so-called metallicity) derived from the two main kinds of emission lines that can be measured in nebular spectra
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Red dwarfs are the most common stars in the galaxy. In recent years they have become key targets in the search for exoplanets. These stars are usually accompanied by rocky planets and due to their low brightness, their habitable zone is close to the star, making it easier to find planets that are within it. GJ 1002 is a red dwarf just one-eighth the mass of the Sun, located only 15.8 light-years away. Using radial velocity measurements from the ESPRESSO and CARMENES spectrographs, we have discovered the presence of two Earth-like and potentially habitable planets. The planets, GJ 1002 b and
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Stellar ages are key to several fields of astrophysics such as exoplanet research, galactic-archeology, and of course stellar physics. Obtaining the ages of stars is however not straightforward and requires stellar modeling. The most widely used technique only requires stellar colors or temperature and surface gravity, but the uncertainties are quite large. This technique is most efficient for stars belonging to clusters, as they were born from the same molecular cloud and share the same ages. In the last decades, based on the study of stellar acoustic waves, asteroseismology became the most
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