We have obtained HST WFPC2 and NICMOS observations in the nuclear region of the closest powerful active galaxy known, NGC 5128 (Centaurus A). Narrow band imaging in the Paalpha line shows an elongated structure around the nucleus which we interpret as a disk of ionized gas, with a 15 pc radius. The disk does not appear to be perpendicular to the

We present intermediate- and low-resolution optical spectroscopy (650-915 nm) of seven faint, very red objects ( 20>I>=17.8 , I-Z>= 0.5) discovered in a CCD-based IZ survey covering an area of 1 deg2 in the central region of the Pleiades open cluster. The observed spectra show that these objects are very cool dwarfs having spectral types in the

We report on the discovery and analysis of a striking neutral sodium gas tail associated with comet C/1995 O1 Hale-Bopp. Sodium D line emission has been observed at heliocentric distance r

We present the near infrared photometry of a new sample of 225 IRAS sources, many of them previously unidentified in the literature, selected because their far infrared colours are similar to those shown by known planetary nebulae. The results obtained are used to establish the main source of near infrared emission. Combining this information with

We propose to obtain [NII]Lambda658.3 nm images of the extended nebulae around the symbiotic binaries CH Cyg {HD182917} and He 2-104 {PK315+09D1} using the WFPC2 camera {+ [OII]Lambda372.8 nm with STIS for CH Cyg}. These large ionized nebulae, one of which has been only recently discovered, trace mass loss episodes spanning a wide range of time

We surveyed a 50 arcmin 2 region in the Virgo cluster core to search for intergalactic planetary nebulae and found 11 candidates in the surveyed area. The measured fluxes of these unresolved sources are consistent with these objects being planetary nebulae from an intergalactic population of stars, although we cannot exclude some minor