Pulsing with History

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Science  08 Feb 2013:
Vol. 339, Issue 6120, pp. 629
DOI: 10.1126/science.339.6120.629-c

Understanding the history of our galaxy depends on having precise measurements of the properties of its stars. This has only been possible for stars that are within around 300 light-years from Earth, but as Miglio et al. demonstrate, advances in asteroseismology—the study of the interior structure of stars through the analysis of their pulsations—mean that this limitation can now be overcome. The authors combined color measurements from the Two Micron All Sky Survey with pulsation data from the CoRoT (Convection Rotation and Planetary Transits) space telescope to obtain the radii, masses, distances, and ages of a sample of just over 2000 red giant stars. These are stars that do not burn hydrogen in their cores any more and that, as a result, have expanded and cooled down; the Sun is expected to become a red giant star in about 5 billion years. The analysis shows that the stars in the sample spread across nearly 50,000 light-years over two separate regions in the disc of our galaxy and that their ages range from 0.3 to 12 billion years, spanning the entire history of the Milky Way. The two regions show significantly different mass distributions. The region higher below the galactic plane has a larger fraction of low-mass and hence older stars, supporting the idea that dynamical processes in the disc increase the velocity dispersion of stars over time.

Mon. Not. R. Astron. Soc. 429, 423 (2013).

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