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From the Cover: The near-infrared nitric oxide nightglow in the upper atmosphere of Venus

Drossart, P.; Piccioni, G.; Mills, F. P. +1 more

The dynamics behind Titan's methane clouds

Mitchell, J. L.; Pierrehumbert, R. T.; Frierson, D. M. W. +1 more

Globular Clusters, Hipparcos, and the Age of the Galaxy

Reid, Neill

We discuss the impact of the results from the recent Hipparcos astrometric satellite on distance estimates of galactic globular clusters. Recalibrating the clusters not only implies a relatively small change in the distance to the Large Magellanic Cloud, and hence a rescaling of several estimates of the Hubble constant, but also leads to significa…

Ultraviolet Spectrum and Probable Chemical Composition of the High-Excitation Planetary Nebula M1-1

Feibelman, Walter A.; Aller, Lawrence H.; Keyes, Charles D.

One of the highest excitation planetary nebulae known, M1-1, was studied with the image-tube scanner on the Shane 3-m telescope at Lick Observatory and with the International Ultraviolet Explorer. Large fractions of abundant elements such as C, N, O, S, and Ar exist in unobservable stages of ionization. Hence, it is difficult to establish the chem…

Spectrum and Chemical Composition of the Remarkable Planetary Nebula NGC 6537

Czyzak, S. J.; Aller, Lawrence H.; Keyes, C. D. +1 more

Observations with the image tube scanner at the Shane 3-m telescope are combined with data obtained with the International Ultraviolet Explorer to assess the spectrum of the remarkable high-excitation planetary nebula NGC 6537. We have analyzed the spectrum of this nitrogen-rich object with the aid of the theoretical nebular models. The models per…

International Ultraviolet Explorer Satellite Observations of Seven High-Excitation Planetary Nebulae

Keyes, C. D.; Aller, L. H.

Observations of seven high-excitation planetary nebulae secured with the International Ultraviolet Explorer (IUE) satellite were combined with extensive ground-based data to obtain electron densities, gas kinetic temperatures, and ionic concentrations. We then employed a network of theoretical model nebulae to estimate the factors by which observe…