We present CCD observations of the galactic globular cluster M15, in the B and V filters. The cluster was reasonably covered, except in its northern region where our observations present a gap. We obtained a Hertzsprung-Russell (HR) diagram for each region observed, and later we produced a combined HR diagram containing more than 3000 stars. We

The integrated Balmer lines of unresolved stellar systems have been widely used as age indicators, since they are sensitive to the temperature of the main sequence turn-off. However, the existence of “non-canonical” stellar stages such as hot horizontal branch stars and blue straggler stars (BSSs) can lead to underestimations of the true stellar

In search of answers to the educational paradigms, in action to educate and inspire students in science and technology, and if each activity where the word education is relevant to define each process that human beings develops in interaction with knowledge.

Aims: Several authors have claimed to detect a significant cross-correlation between microwave WMAP anisotropies and the SDSS galaxy distribution. We repeat these analyses to determine the different cross-correlation uncertainties caused by re-sampling errors and field-to-field fluctuations. The first type of error concerns overlapping sky regions

Context. A search programme for pulsating subdwarf B stars was conducted with the Nordic Optical Telescope on La Palma over 59 nights between 1999 and 2009. Aims: The purpose of the programme was to significantly extend the number of rapidly pulsating sdB stars to better understand the properties of this new group of variable compact stars. Methods

We present a study of the spatial and redshift distributions of Sloan Digital Sky Survey (SDSS) galaxies towards the position of CrB-H, a very deep and extended decrement in the cosmic microwave background (CMB), located within the Corona Borealis supercluster (CrB-SC). It was found in a survey with the Very Small Array (VSA) interferometer at 33