We report the results from an optical imaging survey of proto-planetary nebula candidates using the Hubble Space Telescope (HST). The goals of the survey were to image low surface brightness optical reflection nebulosities around proto-planetary nebulae and to investigate the distribution of the circumstellar dust, which scatters the star light from the central post-asymptotic giant branch star...

We present an Hα + [N II] narrow band image and optical spectra of the galactic nebula PN G218.9-10.7 that has been hardly studied up to now and is suspected to be a planetary nebula. Its morphology is quite unusual: the nebula appears to consist of both symmetric components and asymmetric diffuse ones, and also displays long straight filaments in the east. It rather looks like a combination of...

There is considerable controversy surrounding the nature of M1–78, a compact nebula located beyond the Perseus arm. It was first classified as a planetary nebula and is nowadays generally considered to be a compact H  region.

The most accurate way to measure the energy levels for the O ii 2p 3 ground configuration has been from the forbidden lines in planetary nebulae. We present an analysis of modern planetary nebula data that nicely constrain the splitting within the 2 D term and the separation of this term from the ground 4 S 3/2 level. We extend this method to H ii regions using high-resolution spectroscopy of t...

We investigate spatial distributions of specific dust components in the circumstellar shells of a proto-planetary nebula candidate, HD 179821, and a planetary nebula, BD+30◦3639, by means of spectral imaging. With high-resolution ground-based images and ISO spectra in the midinfrared, we can derive “dust feature only” maps by subtracting synthesized continuum maps from the observed images at th...

We examine the possibility of detecting signatures of surviving Uranus-Neptune-like planets inside planetary nebulae. Planets that are not too close to the stars, orbital separation larger than 5AU, are likely to survive the entire evolution of the star. As the star turns into a planetary nebula, it has a fast wind and a strong ionizing radiation. The interaction of the radiation and wind with ...

We have used infrared polarimetric imaging with NICMOS to determine precisely the position of the star that illuminates (and presumably generated) the bipolar, pre-planetary reflection nebula RAFGL 2688 (the Egg Nebula). The polarimetric data pinpoint the illuminating star, which is not detected directly at wavelengths ≤ 2 μm, at a position well within the dark lane that bisects the nebula, 0. ...