Fall 2014

Reconstructing the Cosmic Evolution of the Chemical Elements

Anna Frebel

The chemical elements are created in nuclear fusion processes in the hot and dense cores of stars. The energy generated through nucleosynthesis allows stars to shine for billions of years. When these stars explode as massive supernovae, the newly made elements are expelled, chemically enriching the surrounding regions. Subsequent generations of stars are formed from gas that is slightly more element-enriched than that from which previous stars formed. This chemical evolution can be traced back to its beginning soon after the Big Bang by studying the oldest and most metal-poor stars still observable in the Milky Way today. Through chemical analysis, they provide the only available tool for gaining information about the nature of the short-lived first stars and their supernova explosions more than thirteen billion years ago. These events set in motion the transformation of the pristine universe into a rich cosmos of chemically diverse planets, stars, and galaxies.

ANNA FREBEL is the Silverman (1968) Family Career Development Professor in the Physics Department at the Massachusetts Institute of Technology and a member of the MIT Kavli Institute for Astrophysics and Space Research. Her research interests include stellar archaeology and near-field cosmology. Her work has recently appeared in Nature, The Astronomical Journal, and Astronomy and Astrophysics, among other journals; and in the volume Planets, Stars, and Stellar Systems (ed. Gerard Gilmore, 2012).

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