The authors present the results of a statistical analysis of the penumbra of sunspots. The intensity distribution, and several parameters derived from it, is analysed at different heliocentric angles and positions on the spot. It has revealed, on the one hand, that a two-component model is compatible with the observations and that both components

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SE HA REALIZADO UN ESTUDIO DETALLADO DE LA COMPOSICION QUIMICA EN LAS NEBULOSAS PLANETARIAS A78, NGC246, NGC650, NGC1360, NGC1514, NGC6578, NGC6772, NGC6781, NGC6804, NGC6853, NGC6894, NGC7008, NGC7293, JN1, NGC6543 Y NGC6826, GRACIAS A LA UTILIZACION DE ESPECTROSCOPIA DE RENDIJA LARGA. CON LA EXCEPCION DE A78, NGC6543 Y NGCL6826, SE ENCONTRO QUE

Using accurate radial velocity observations of integral sunlight, the background solar velocity noise has been measured at different frequencies of interest for solar oscillations within a frequency interval between 10-7 and 10-2Hz. Comparison with a numerical model, simulating the most important solar processes: granulation, mesogranulation

Following earlier work by Shields and Searle and by Mathis, the authors define a radiation softness parameter η = (O+/O++)(S++/S+), which they recommend as a criterion of effective temperature of the ionizing star(s) of H II regions that is relatively insensitive to chemical composition and ionization conditions found in optically observed nebulae

The age dependence of the recently described asymmetry of penumbrae of large stable sunspots was analyzed. Young sunspots showed shorter eastern penumbrae, which differed by a maximum of + or - 10 percent from their mean width. For older sunspots the western penumbrae became smaller than the mean penumbra, reaching differences of 20 percent for