Stellar magnetic activity results from the interaction between stellar magnetic field and the plasma in photosphere, chromosphere, and corona. This activity produces well known phenomena, such as flares, spots, faculae, and prominences, observed in stars of almost every type and mass. This activity is typically studied by analyzing spectroscopic activity indicators produced by these phenomena, such as the H and
In the last years, several organic molecules, some of which of prebiotic interest, have been observed in different astronomical environments. For instance, Acetonitrile CH3CN was detected in the molecular cloud Sag B2 and in the protostar MWC480; formamide (a building block for sugars and amino-acids) was detected in some outer galaxies and in the protostar SVS13-A (in this case together
The Sun has an intense magnetic activity which produces transient phenomena such as flares, coronal mass ejections (CMEs), sunspots, etc…, with CMEs being the most energetic phenomena associated with the solar magnetic activity. CMEs consist in rapid ejections of coronal plasma, which are triggered by the recombination of the magnetic field lines that also produce solar flares. During solar flares,
The stellar magnetic activity can produce an important emission of energetic X-ray and UV radiation. This emission is typically variable, both because the magnetic activity changes over short time scales, and because it decreases during stellar evolution. For instance, solar-type stars in the pre-main sequence phase (i.e. younger than 30 million years) are thousand times brighter in X-rays than main
T Tauri stars are young (typically younger than 10 million years) stars surrounded by a protoplanetary disk, which is a disk of gas and dust orbiting around the star and that eventually can evolve in planetary systems. Despite these stars have already accreted most of their mass, they can still accrete some mass from their protoplanetary disks. The accretion process
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
“Protostars” are stars a few million years old, which are still accreting gas and contracting for their own gravity, and whose nucleus has not reached yet the temperature and pressure necessary for the onset of thermonuclear reactions. The youngest protostars are still surrounded by a protoplanetary disk of gas and dust (class II protostars) or even by an accreting envelope
Stars form from the gravitational collapse of large interstellar clouds. During the process, the clouds fragment in smaller clouds, forming clusters and associations of stars counting from few tens to several hundred thousands stars. The star formation process typically is not a monolithic process, e.g. with a single large event of star formation occurring rapidly and forming all the stars
Observations of the Sun show that our star hosts transient and violent phenomena which are due to the interaction between the plasma and the magnetic field produced in the interior of the Sun. Typical examples of this “magnetic activity” are the sunspots in the photosphere and the protuberances in the chromosphere. The solar flares are among those phenomena associated with
Low mass star (in particular M-type star, with a mass between 0.075 and 0.5 solar masses) are typical targets for the search and study of exoplanets. In these stars, in fact, the radial velocity method is more efficient than in stars with higher mass. Radial velocity consists in detecting periodic oscillations in the stellar spectra due to the motion of
