This volume documents the contributions presented at the 4th Scientific Meeting of the Spanish Astronomical Society (SEA). Covering a wide range of topics, the 146 contributed papers give a comprehensive overview of the current state of Spanish astronomy. The Proceedings include special reviews dealing with the cosmological information obtained from galaxy spectra, supernovae at high redshift, black holes, dynamics of galaxy interactions, and non-LTE inversion of spectral lines. The contents of these Proceedings thus reflect the broad interests of the Spanish astronomical community. The symbolic significance of these proceedings can hardly be exaggerated, since here, for the second time, the SEA publishes the proceedings of its own scientific meeting. This book is recommended to professional astronomers and astronomy graduate students worldwide.