NGC 6791 is a well studied open cluster that is so close to us that it can be imaged down to very faint luminosities. Two different ages have been proposed for this cluster, one based on the white dwarf luminosity function and one derived from its main-sequence stars. The discrepancy in age is now resolved by the finding that, as theoretically anticipated, physical separation processes occur in the core of white dwarfs.
- Enrique GarcÃa-Berro
- Santiago Torres
- Jordi Isern
