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Echography of young stars reveals their evolution

Science  01 Aug 2014:
Vol. 345, Issue 6196, pp. 550-553
DOI: 10.1126/science.1253645

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A finger on the pulse of young stars

Adolescent stars quiver and quake before the onset of nuclear fusion in their cores. Zwintz et al. confirm theoretical predictions that the frequency of the seismic oscillations in a given star is tied to its evolutionary status (see the Perspective by Stahler and Palla). As the protostar evolves and contracts, growing hotter and denser, it pulsates faster. Though previously applied only to aging stars, asteroseismology now offers a powerful tool for discerning the ages of very young stars. The relative timing of star formation within young clusters especially benefits from this refinement, as stars there are often tagged with one blanket age.

Science, this issue p. 550; see also p. 514

Abstract

We demonstrate that a seismic analysis of stars in their earliest evolutionary phases is a powerful method with which to identify young stars and distinguish their evolutionary states. The early star that is born from the gravitational collapse of a molecular cloud reaches at some point sufficient temperature, mass, and luminosity to be detected. Accretion stops, and the pre–main sequence star that emerges is nearly fully convective and chemically homogeneous. It will continue to contract gravitationally until the density and temperature in the core are high enough to start nuclear burning of hydrogen. We show that there is a relationship for a sample of young stars between detected pulsation properties and their evolutionary status, illustrating the potential of asteroseismology for the early evolutionary phases.

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