Stars form from the gravitational contraction of large gas clouds. This process may occur in two different modes: It may be fast, with a characteristic timescale dictated by the free fall of gas onto the forming stars, or it may be slow, sustained by turbulence and magnetic field. In the former case stars form over a short period, while in
The study of the chemical abundances of stars with different age and position in the Milky Way provide crucial information on the formation and evolution of our Galaxy. In particular, heavy elements (i.e. those with the atomic number Z > 30) are produced by the successive capture of neutrons by lighter elements. This occurs by two processes, the slow s-process
of Mario Giuseppe Guarcello ( follow mguarce) We are living a golden age for the research on stellar clusters and their structure, formation and evolution. This thanks to the satellite Gaia of the European Space Agency, which will provide position and radial velocity of over one billion stars with unprecedented precision, and the project Gaia-ESO Survey, an ambitious spectroscopic
Despite the stars in our Galaxy typically formed in stellar clusters, only a small fraction of them today is observed associated with a cluster. This led to the conclusion that stellar clusters typically disperse in 10-100 million years. Two mechanisms are thought to be responsible for the dispersion of stellar clusters. According to the model of the “residual gas expulsion”,
The study of star-forming regions of our Galaxy is one of the main research topic of the Astronomical Observatory of Palermo. This because they can provide crucial information on how large molecular clouds collapse and form stars, on the early stellar evolutionary stages, on the formation of planetary systems, the formation and dispersion of protoplanetary disks, and the history and
The study of binary systems plays an important role in several fields of astronomy such as stellar evolution and galactic archeology since it allows direct measurements of stellar parameters such as masses, radii, and luminosities. Multiple stellar systems have typically small angular separation and thus they are not resolved by direct imaging. In these cases spectroscopy is a powerful tool
Not all the archaeologists do their studies digging holes or classifying artifacts in dusty museums… some of them actually use telescopes… Galactic archeology is a branch of astronomy dedicated to the study of the formation and evolution of the components of our Galaxy (bulge, bar, disc and halo) by analyzing ages, dynamics, and chemical abundances of stars. Not an easy
Stars more massive than 9 solar masses are efficient chemical labs, where hydrogen and helium are synthesized into other chemical elements, such as oxygen, carbon, and silicon. When these stars explode as supernovae (type I or “core-collpase” supernovae), these chemical elements are ejected into space, enriching the interstellar medium and being in future available to form new generations of stars.
Massive stars are enormous chemical laboratories where heavy chemical elements are synthesized. For instance, the alpha-elements (O, Mg, Si, Ca, and Ti) are produced by nucleosynthetic processes in the interior of massive stars. Moreover, the lifetime of massive stars is much shorter than that of low mass stars: few million years for the former compared to several billion of years
di Mario Giuseppe Guarcello ( segui mguarce) Esistono vari modelli che cercano di spiegare la formazione e l’evoluzione del disco sottile della Via Lattea, della sua popolazione stellare e dei bracci a spirale. Uno dei parametri fondamentali per il processo di formazione stellare nel disco, la distribuzione di massa delle stelle, l’evoluzione stellare e la migrazione lungo il disco
