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

In a statistical study of the decay of individual sunspots based on DPR data we find that the mean instantaneous area decay rate is related to the spot radius r and the maximal radius r0 as D=C r/r0, C=32.0 +- 0.26 MSH/day. This implies that sunspots on the mean follow a parabolic decay law; the traditional linear decay law is excluded by the data

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