In order to test the expansion of the universe and its geometry, we carry out an Alcock-Paczyński cosmological test, that is, an evaluation of the ratio of observed angular size to radial/redshift size. The main advantage of this test is that it does not depend on the evolution of the galaxies but only on the geometry of the universe. However, the

We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the fine guidance sensor 1R (FGS1r) on the Hubble Space Telescope. FGS1r is able to resolve binary systems with a magnitude difference ΔV 4 down to separations as small as 0.''01. The sample includes 58 of the brighter

Solar magnetic indices are used to model the solar irradiance and ultimately to forecast it. However, the observation of such indices is generally limited to the Earth-facing hemisphere of the Sun. Seismic maps of the far side of the Sun have proven their capability to locate and track medium-large active regions at the non-visible hemisphere. We

Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some Planetary Nebulae (PNe) now enable us to study the DIBs in fullerene-rich space environments. We have studied the presence of DIBs in the optical spectra (

The outburst of the unusual transient V838 Monocerotis in 2002 illuminated surrounding interstellar dust, producing the most spectacular light echoes in astronomical history. The echoes remained visible for several years. Because of the light-echo geometry, each imaging observation corresponds uniquely to a well-defined paraboloidal region of space

Aims: We derive the thermal inertia of 2008 EV5, the baseline target for the Marco Polo-R mission proposal, and infer information about the size of the particles on its surface. Methods: Values of thermal inertia were obtained by fitting an asteroid thermophysical model to NASA's Wide-field Infrared Survey Explorer (WISE) infrared data. Grain size