We investigate the cosmology of x-matter with pressure, px, and density, ρx, related by px=w0ργx(w0 0). For γ >1, this x-matter behaves like a cosmological constant when a

Ursa Minor (UMi) is one of the closest satellites of the Milky Way (d=69 kpc). It is possibly a disrupted dSph interacting with the external Galactic halo. This makes its study quite necessary in the forementioned context. In this paper we present preliminary results of a wide field photometry survey of UMi and discuss the presence of an

IAUC 7086 available at Central Bureau for Astronomical Telegrams.

Very high-resolution (R ~ 110 000) spectroscopic observations of the very low-mass star VB 8, obtained with the Utrecht Echelle spectrograph (UES), are presented. A flare occurred during the third of a series of four consecutive spectra. This event produced significant enhancement in the strength of the emission lines of He i D3 and Hα in VB 8, as

Leo I and Leo II are the two most remote dSph galaxies satellites of the Milky Way, situated at about 250 Kpc of it. They are objects of similar size and low metallicity, but their star formation histories appear to be fundamentally different. The very deep HST color-magnitude diagrams (CMDs) of these galaxies reach the position of the oldest

The SFH of galaxies can be studied with detail in nearby systems which are resolvable into individual stars. In such case, the color-magnitude (CM) diagram can be plotted. Perhaps, the most powerful method nowadays available for the study of the SFH of galaxies is to compare their observed CM diagrams with sets of synthetic CM diagrams computed