The beat of young stars

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Science  01 Aug 2014:
Vol. 345, Issue 6196, pp. 514-515
DOI: 10.1126/science.1257301

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A star is a ball of gas held together by the compressive force of self-gravity and supported from within by thermal pressure. For most of a star's life, this dynamical balance is stable; perturbing the star does not lead to explosion or collapse, but to oscillation about its equilibrium configuration. Such perturbations arise constantly from small motions within the star itself. Consequently, stars of many evolutionary phases exhibit periodic fluctuations in their luminosity (see the first figure). On page 550 of this issue, Zwintz et al. (1) report on oscillations of stars so young that they are not yet fusing hydrogen into helium. Expanding on earlier studies of such pre–main-sequence stars (2), Zwintz et al. find that the observed frequencies of oscillation of a star vary with its age, and do so in the way that theory predicts. Thus, the oscillations potentially provide a new chronometer—something greatly needed in the field of early stellar evolution.