Number of stars in the Sun's birth cluster revisited

The Sun is thought to have been formed within a star cluster. The coexistence of Al-26-rich and Al-26-poor calcium-aluminum-rich inclusions indicates that a direct injection of Al-26-rich materials from a nearby core-collapse supernova would be expected to occur in the first 10(5) years of the existence of the Solar System. Therefore, at least one core-collapse supernova ought to occur within the duration of star formation in the Sun's birth cluster. Here, we revisit the number of stars in the Sun's birth cluster from the point of view of the probability of experiencing at least one core-collapse supernova within the finite duration of star formation within the birth cluster. We find that the number of stars in the birth cluster may be significantly greater than that previously considered, depending on the duration of star formation.