A white dwarf cooling age of 8 Gyr for NGC 6791 from physical separation processes

NGC 6791 is a well studied open cluster that it is so close to us that can be imaged down to very faint luminosities. The main-sequence turn-off age (∼8 Gyr) and the age derived from the termination of the white dwarf cooling sequence (∼6 Gyr) are very different. One possible explanation is that as...

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Bibliographic Details
Published in:Nature (London) 2010-05, Vol.465 (7295), p.194-196
Main Authors: Torres, Santiago, Córsico, Alejandro H, Althaus, Leandro G, Rohrmann, René D, Isern, Jordi, García-Berro, Enrique, Renedo, Isabel, Salaris, Maurizio, Lorén-Aguilar, Pablo
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Evolution
Exact sciences and technology
Faint blue stars (including blue stragglers), white dwarfs, degenerate stars, nuclei of planetary nebulae
Normal stars (by class): general or individual
Observations
Open clusters
Open clusters in the milky way
Space telescopes
Star & galaxy formation
Stars
Stars & galaxies
Stellar clusters and associations
Stellar systems. Galactic and extragalactic objects and systems. The universe
White dwarfs
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Summary:NGC 6791 is a well studied open cluster that it is so close to us that can be imaged down to very faint luminosities. The main-sequence turn-off age (∼8 Gyr) and the age derived from the termination of the white dwarf cooling sequence (∼6 Gyr) are very different. One possible explanation is that as white dwarfs cool, one of the ashes of helium burning, 22Ne, sinks in the deep interior of these stars. At lower temperatures, white dwarfs are expected to crystallize and phase separation of the main constituents of the core of a typical white dwarf (12C and 16O) is expected to occur. This sequence of events is expected to introduce long delays in the cooling times, but has not hitherto been proven. Here we report that, as theoretically anticipated, physical separation processes occur in the cores of white dwarfs, resolving the age discrepancy for NGC 6791.
ISSN:0028-0836
1476-4687
DOI:10.1038/nature09045