The Hipparcos mission has made it possible to constrain the positions of nearby field stars in the colour-magnitude diagram with very high accuracy. These positions can be compared with the predictions of stellar evolutionary calculations to provide information on the basic parameters of the stars: masses, radii, effective temperatures, ages, and

High-resolution spectra of a sample of all known stars more luminous than MV=+6.5 and closer than 15 parsecs are being analyzed spectroscopically in order to derive their effective temperatures and surface gravities. These spectra are taken from the database of "A Spectroscopic Survey of Stars in the Solar Neighborhood". The analysis utilizes a

The ratios between the amplitudes of p-modes measured simultaneously in the Na and K resonance lines are compared with the expected ratios for adiabatic waves at two different levels in the atmosphere. The results agree within errors with the energy decaying solution for the waves at the photosphere.

We present optical and near-infrared colour maps of the central regions of bulges of S0 and spiral galaxies obtained with WFPC2 and NICMOS on the Hubble Space Telescope (HST). By combined use of HST and ground-based data, the colour information spans a region from a few tens of pc to a few kpc. In almost all galaxies, the colour profiles in the

We present results on the study of 24 bulges of Sa galaxies observed with the integral-field unit SAURON at the William Herschel Telescope. Here we review some of the main features observed in our maps in terms of their kinematics and stellar populations, and unveil a rather complex picture in which the centers of spiral galaxies are made of

We present photometry for globular and open cluster stars observed with the Sloan Digital Sky Survey (SDSS). In order to exploit the over 100 million stellar objects with r