Aims: We present a portrait of the active Centaur P/2010 C1 (Scotti), observed with a well developed comet-like activity (central diffuse coma condensation and an extended sharp tail-like structure) at the heliocentric distance of rh = 5.5 AU. Methods: We analyse multicolour (B, V, R, and I) images taken at the TNG telescope to characterise the

This thesis focuses on the quantitative spectroscopic study of the O dwarf population in 30 Doradus (Large Magellanic Cloud, LMC), aiming at clarifying some long-standing open questions about the formation, evolution and physical properties of O stars during their main-sequence phase, where they spend most of their lifetime. This work has been

The fraction of star-forming to quiescent dwarf galaxies varies from almost infinity in the field to zero in the centers of rich galaxy clusters. What is causing this pronounced morphology-density relation? What do quiescent dwarf galaxies look like when studied in detail, and what conclusions can be drawn about their formation mechanism? Here we

We present the result of a study on the expansion properties and internal kinematics of round/elliptical planetary nebulae of the Milky Way disk, the halo, and of the globular cluster M 15. The purpose of this study is to considerably enlarge the small sample of nebulae with precisely determined expansion properties (Schönberner et al. \cite{SJSPCA

Context. K-means is a clustering algorithm that has been used to classify large datasets in astronomical databases. It is an unsupervised method, able to cope very different types of problems. Aims: We check whether a variant of the algorithm called single pass k-means can be used as a fast alternative to the traditional k-means. Methods: The