Based on our large and homogeneous photometric database of globular cluster observations taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope, a set of distance and reddening independent relative age indicators have been measured. The high quality of the color magnitude diagrams (CMDs) allows us to explore several variations

The HST/ACS Survey of Galactic globular clusters is a Treasury project designed to obtain photometry with S/N ≥10 for main sequence stars with masses ≥ 0.2M&sun; in a large sample of globulars using the Advanced Camera for Surveys (ACS) Wide Field Channel. We plan to use these data to address a range of astrophysical questions. Here we present new

Using data collected as part of the Hubble Space Telescope Advanced Camera for Surveys (ACS) study of Galactic gobular clusters, we present photometry and luminosity functions (LFs) extending several magnitudes below the main sequence turn off for a sample of Galactic globular clusters. These clusters have been selected from the larger ACS survey

The HST/ACS GGC Survey provides reliable photometry from 6 magnitudes below the main sequence turn-off to the level of the horizontal branch ( 3.5 magnitudes brighter than the turn-off) for 65 Galactic globular clusters. The absolute ages of a sub-sample of those clusters, which have low reddenings and well determined chemical compositions, have

This paper reviews some of the most recent advances in the application of the Hanle effect to solar physics, and how these developments are allowing us to explore the magnetism of the photospheric regions that look ``empty'' in solar magnetograms--that is, the Sun's ``hidden'' magnetism. In particular, we show how a joint analysis of the Hanle

We present a theoretical investigation on the influence of the magnetic field on the linear and circular polarization of the Ba II D2 line at 4554 Å, through the Hanle and Zeeman effects. We show in particular the existence of a differential magnetic sensitivity of the three-peak structure of the Q/I profile observed for this line, which is of