Resumen
One of the fundamental questions in modern astronomy is how the Solar System formed. We now recognize that the majority of stars in the Galaxy formed in vast regions called OB associations, which exhibit all stages of the star formation process, from very young, embedded clusters, to older, fully exposed young stars. Large scale surveys in these regions have revealed that low-mass stars exist wherever high-mass stars have recently formed. The spatial distribution and ages of low-mass young stars provide support to the idea that the parent molecular clouds are transient structures, with lifetimes of 10 Myr or less, and that star formation is a rapid and often triggered process. Studies of circumstellar disks in these young populations indicate that the duration of the planet-forming phase is on average 10 Myr or less.
