L’evoluzione finale delle stelle massicce presenta ancora diversi punti da chiarire. Sin dal 1975 è stato proposto che le stelle di Wolf-Rayet (WR), stelle di grande massa che hanno espulso i propri strati esterni ricchi di idrogeno ed elio, caratterizzati da temperature elevatissime e venti a migliaia di km/s, siano il prodotto di perdite di massa estremamente intense. Tuttavia, solo stelle con
Spesso è difficile stabilire se attorno a una stella orbiti un pianeta gassoso, una nana bruna o una stella di piccola massa. Tuttavia, una tecnica che combina misure di velocità radiale e astrometriche può fornire indicazioni affidabili in merito. Alcuni studi condotti su campioni di stelle con esopianeti indicano che, attorno a stelle di tipo solare, la probabilità di
Every sci-fi enthusiast, especially Star Wars fans, has wondered whether planets orbiting two stars, like Tatooine, can exist in reality. This is actually an important question in astronomy: It has been estimated that in the Milky Way, one-third of low-mass stars are in binary systems. Therefore, to fully understand the population of planets in our Galaxy, it is necessary to
Several stellar phenomena and evolutionary processes are connected to their magnetic fields. The mechanisms that allow stars to produce their magnetic fields depend on their internal structure and stellar properties. One dominant property is stellar rotation: the faster stars rotate, the more intense their magnetic field and magnetic activity. Since stellar rotation declines with age, it is not surprising that
After the Big Bang, the Universe contained only hydrogen, helium, and a very small fraction of lithium. After that, stars, mainly the most massive ones, were responsible for the chemical enrichment of the Universe. In fact, stars produce energy by synthetizing chemical elements in their cores. These elements are then redistributed in the interstellar medium when stars end their evolution.
In our Galaxy, a large fraction of stars is part of binary systems. For instance, the study of Duquennoy & Mayor (1991) suggests a binary fraction of 57% for solar type stars. A slightly smaller binary fraction is expected for less massive stars. Among pre-Main Sequence stars, several binary systems are known to host a circumbinary disk. These disks are
di Mario Giuseppe Guarcello ( follow mguarce) Type Ia supernovae are particularly important in cosmology since they allow us precise measurements of the hosting galaxies. These supernovae are not triggered by the collapse of the core of massive stars, such as the “core-collapse supernovae”. They are instead due to the thermonuclear explosion of a white dwarf in close binary
