Regions of star formation, star clusters and young stars
Today, the projects underway in this branch of astrophysics are mainly directed to the study of very young stars in regions of star formation close to the Sun. These allow the physical mechanisms at work in the early phases of stellar evolution to be understood, from the proto-stellar nuclei to the ignition of nuclear fusion within the stars. The observations and the comparison of the properties of young stars at various distances within our galaxy, or nearby galaxies, allows us to understand the environmental effects on both single stars and the global properties, such as the initial mass function, which is one of the fundamental parameters in the study of stellar evolution. From the determination of the properties of individual young stars it is possible to understand the much more violent phenomena observed in external galaxies.
The study of the evolution of the circumstellar disks of young stars is important for the understanding of the mechanisms and conditions necessary for the formation of planetary systems, their evolution and their characteristics.
Ultimately, regions of star formation and open clusters provide natural laboratories for the study of the stars, allowing the determination of certain fundamental parameters such as the distance, age and chemical composition, so that the role of other factors, such as the mass and rotation, can be understood.
The study of young stars is necessarily multi-band: the various components of a young stellar system are evident in different parts of the electromagnetic spectrum (particularly the infrared, visible and X-rays). As a consequence, both ground based and space facilities of various sizes are used, depending on the scientific goal. For example, medium sized ground-based telescopes are ideal for photometric monitoring and the observation of bright stars, while the larger telescopes allow fainter stars and brown dwarfs to be observed. Of the telescopes used we highlight the use of the Telescopio Nazionale Galileo (TNG) in the Canaries, the European Southern Observatory (ESO) telescopes at La Silla in Chile, the Very Large Telescope (VLT) and the GranTeCan that has only just become available to the scientific community. Similarly, extensive use is made of infrared and X-ray space telescopes (Spitzer, HST, CoRot, Chandra, XMM/Newton, Herschel).
Another aspect is the the study of so-called YSOs (Young Stellar Objects), that is, stars in their very first evolutionary phases, in various regions of star formation and environments. Italian researchers are heavily involved as principal investigators (PI) in observations to determine certain properties of these YSOs.
Many young stars show the phenomenon of material jets, and the study of their physical, chemical and kinematic properties is another important field of study where Italian INAF researchers have taken a leadership role. This has been both in the development of diagnostic methods based on optical and infrared spectral lines and in observations using the latest generation of instruments, such as integral field spectrographs and the detectors on board the HST. Some of these material jets emit in the X-ray band, and a numerical model is currently under development to explain this emission.
Lastly, the study of more distant regions continues via the study of a large number of hot, massive stars, that can influence the formation and evolution of new stars.
