The linear polarization produced by scattering processes in the spectral lines of the IR triplet of Ca II can be observed near the edge of the solar disk. The cause of this polarization was considered a true enigma until the year 2003, in which IAC researchers could carry out sophisticated calculations based on the quantum theory of the spectral line polarization. In this way, they could demonstrate that the physical origin of the enigmatic polarization is the presence of "atomic polarization" in the lower levels of such spectral lines, which produces dichroism (i.e., selective absorption of the polarization components of the radiation beam that propagates towards the observer) without the need of a magnetic field. This result is important because it provides a way to detect extremely weak magnetic fields in Astrophysics, both in the solar atmosphere and in other astrophysical plasmas (e.g., in the atmospheres of supernovae).
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Accretion disks around compact objects are expected to enter an unstable phase at high luminosity. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole. Although there are hints of these cycles in a few isolated cases, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle. Here
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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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In the 90s, the COBE satellite discovered that not all the microwave emission from our Galaxy behaved as expected. Part of this signal was later assigned to a fresh new emission component, spatially correlated with the Galactic dust emission, which showed greater importance in the microwave range of frequencies. It has been named since as “anomalous microwave emission”, or AME. The current main hypothesis to explain the AME origin is that it is emitted by small dust particles which undergo fast spinning movements. In Fernández-Torreiro et al. (2023), we study the observational properties of
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