Hundreds of circumstellar disks in the Orion nebula are being rapidly destroyed by the intense ultraviolet radiation produced by nearby bright stars. These young, million-year-old disks may not survive long enough to form planetary systems. Nevertheless, the first stage of planet formation-the growth of dust grains into larger particles-may have begun in these systems. Observational evidence fo...

WeBo 1 (PN G135.6+01.0), a previously unrecognized planetary nebula with a remarkable thinring morphology, was discovered serendipitously on Digitized Sky Survey images. The central star is found to be a late-type giant with overabundances of carbon and s-process elements. The giant is chromospherically active and photometrically variable, with a probable period of 4.7 days; this suggests that ...

The internal velocity fields of planetary nebulae are studied with a resolution of 5 km s. We analyze deep echelle spectra from three nebulae in the Bulge, the Sagittarius Dwarf and the SMC. No effects of metallicity is seen, except possibly a slower onset of the fast wind from the central star. Robust evidence is found for the existence of a high-velocity shock at the inner edges of the nebula...

NGC1360 is a large planetary nebula (PN) without an obvious shell morphology. We have analyzed Hα images and high-dispersion echelle spectra of NGC1360 in order to construct spatio-kinematic models and to determine its density distribution. The best-fit model indicates that NGC 1360 is a prolate ellipsoidal shell whose major axis is twice as long as its minor axis and is tilted by 60 with respe...

The best constraints on dark halo properties of elliptical galaxies come from large radii; however, observations at these radii are difficult due to the faint stellar light and/or sparse kinematic tracers (i.e., globular clusters, planetary nebulae). We present line-of-sight stellar velocity distributions of elliptical galaxy NGC 821 obtained to approximately 100 (over 2 effective radii) with l...

The gas turbulence in planetary nebulae: quantification and multi-D maps from long-slit, wide-spectral range echellogram. ABSTRACT Context. This methodological paper is part of a short series dedicated to the long-standing astronomical problem of de-projecting the bi-dimensional, apparent morphology of a three-dimensional distribution of gas. Aims. We focus on the quantification and spatial rec...

Mass-independent O isotopic fractionations in CAIs have long been attributed to the mixing of nucleosynthetic components, but no other major elements have shown such nucleosynthetic contribution arguing against this hypothesis. Hence, Clayton (1) proposed that self-shielding of CO in the proto-solar nebula resulted in the preferential production of O isotopes, which were then accommodated in so...