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2012 Annual Science Report

Arizona State University Reporting  |  SEP 2011 – AUG 2012

Astrophysical Controls on the Elements of Life, Task 6: Determine Which Elemental or Isotopic Ratios Correlate With Key Elements

Project Summary

Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. We study the formation and composition of structures in supernova explosions that deliver bioessential elements to material that will form new stars and planets. We use the abundance of the element europium to estimate the abundances of uranium and thorium in nearby stellar systems and their effects on the thermal evolution of extrasolar planets. The relative abundances of common elements vary substantially among nearby stars, and we find that the impact of this on a star’s evolution can change the amount of time its planets are habitable by billions of years.

4 Institutions
3 Teams
1 Publication
0 Field Sites
Field Sites

Project Progress

Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. Patrick Young (ASU), Carola Ellinger (University of Texas at Arlington), Chris Fryer (Los Alamos), and Gabe Rockefeller (Los Alamos) post-processed a large suite of 3D supernova simulations to find detailed, spatially resolved nucleosynthetic yields. We developed a method for quantifying the physical scales of the structures formed in the supernova explosion that deliver newly synthesized elements to the interstellar medium, proto-stellar cores, and proto-planetary disks. The simulations now extend well into the period of interaction of the supernova with the surrounding gaseous environment. Liubin Pan, Steve Desch, Frank Timmes, and Evan Scannapieco (ASU) simulated impact of supernova bullets into molecular clouds and show that when cooling of gas is included, dense clumps penetrate and mix efficiently. This addition of material can significantly change the abundances in the molecular cloud.

Bryce Carande, Patrick Young, and Allen MacNamara (ASU) have presented results of using parameterized convection models of planetary interiors and thermal evolution of exoplanets. The long-lived radioactive isotope abundances for these models are inferred from observations of Europium in nearby sun-like stars, which trace well the U and Th abundances. Michael Pagano is finding abundances for stars that are targets of radial velocity planet searches. The analysis is nearly complete for stars in the sample that are known to host exoplanets. These abundances will be used to inform work by Dan Shim (ASU) on mineralogy and planetary interiors for exoplanets in systems with non-solar compositions. Patrick Young and Kelley Liebst (ASU) have created stellar models of a range of stars for variable elemental abundance ratios with the TYCHO stellar evolution code. The variation in abundance ratios, particularly O/Fe, observed in nearby stars has a substantial effect on the evolution of habitable zones. For an Earth-like planet in a one astronomical unit orbit, the time spent in the star’s habitable zone can range from 3.5 to 9 billion years.