Some of the 4903 exoplanets discovered and confirmed so far (https://exoplanets.nasa.gov/) orbit very close to their stars. We learnt with the very first planet discovered around a star different than the Sun (51 Pegasi b, discovered in 1995) that planets with very close orbits are possible in nature. 51 Pegasi b, in fact, orbits at about 0.05 Astronomical Units (AU,
The atmosphere of the Sun hosts a rich variety of magnetic phenomena, which are the consequence of the interaction between the solar magnetic field and the hot and highly ionized solar gas (plasma). The main magnetic phenomena occurring in the photosphere are the sunspots. They appear as dark spots in the bright solar surface, which correspond to regions with intense
We typically observe phenomena due to the interaction between the magnetic field of Sun and its plasma, which is the hot (from 5600 K in photosphere to million degrees in the corona) gas with a high level of ionization, on the photosphere, chromosphere, and corona of our star. Some of these magnetic phenomena are starspots, faculae, prominences, and flares. In particular, solar
Planet formation occurs in disk-like structures, called “protoplanetary disks”, observed around very young stars. The dispersal timescale of these disks (being typically 3-5 million of years) sets an important limit to the planet formation timescales predicted by theoretical models. The widely accepted model that explains the formation of the gaseous giant planets, such as Jupiter, is the “core-accretion model“. This
Our knowledge of stellar evolution relies on our capability of obtained precise measurements of stellar ages, a challenging task for isolated stars which, however, is typically easier for stars in clusters. In fact, clusters contain stars formed more or less simultaneously from a single molecular cloud. This means that they represent coeval samples of stars with different masses, which allow
LBV (Luminous Blue Variable) stars are massive and unstable stars characterized by large mass-lost due to intense stellar winds and aperiodic bursts. Due to their instability, LBV stars are also variable, with quasi-periodic oscillations of their luminosity of the order of 0.5-2 magnitudes. Typical examples of this class of stars are: the supergiant S Doradus in the Large Magellanic Clouds,
In the last years several observational surveys were designed in order to detect stellar mass black holes, including both those which are actively accreting and black holes in a quiescent status. These observations are crucial to understand the real extent of the population of black holes in the Milky Way, and to understand the formation of massive stellar black holes
The study of the architecture of planetary systems, and in particular that of the spin-orbit angle (which is the inclination of the planetary orbit with respect to the stellar rotation axis) can unveil important details on the dynamical evolution of planetary systems. In particular, young planets typically migrate radially, changing their distance to the host star and interacting with the
To date (October 2021, data from https://exoplanets.nasa.gov/), astronomer discovered enough exoplanets (in excess of 4500) to allow not only analysis of individual planets, but also detailed studies of the whole exoplanets population. These studies are necessary to fully understand the process of planets formation, the evolution of planets, the chemical composition and physical properties of planets atmospheres, and how the forming
About 20% of the exoplanets discovered so far (October 2021) were found with measurements of radial velocity (data from https://exoplanets.nasa.gov/). This method is based on spectroscopic observations of stars with planets, from which it is possible to measure the Doppler effect produced by periodic oscillations of the star, due to the gravitational attraction between star and planet along the orbit of
