We use the recent results on solar acoustic modes coming from GOLF and MDI, to demonstrate that we improve the quality of the inversion of the sound speed and the density by avoiding several biases coming from the turbulent surface. The present accuracy allows a quantitative discussion on the physics of the solar nuclear core. We now exclude

VIRGO-SPM is a helioseismic instrument on board SOHO that observe the disk-integrated sunlight irradiance at three different colours (red, green and blue). In this work the differences of the p-modes parameters are studied along the solar activity cycle.

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The GTC is a high performance 10-m class telescope to be installed at the Roque de los Muchachos Observatory (ORM), on the island of La Palma. First light is planned for end 2002 and the start of full scientific operations for end 2003. The GTC top level science requirements are to achieve: (1) a major improvement in limiting magnitude between 0.3

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We investigate the use of surface brightness fluctuations (SBF) measurements in optical and near-IR bandpasses for both stellar population and distance studies. New V-band SBF data are reported for five galaxies in the Fornax cluster and combined with literature data to define a V-band SBF distance indicator, calibrated against Cepheid distances to