Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 7 March 2003:
Vol. 299. no. 5612, pp. 1552 - 1555
DOI: 10.1126/science.1080866
Prev | Table of Contents | Next

Reports

The Cosmic Production of Helium

Raul Jimenez,1* Chris Flynn,23 James MacDonald,4 Brad K. Gibson3

We estimate the cosmic production rate of helium relative to metals (Delta Y/Delta Z) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting value is Delta Y/Delta Z = 2.1 ± 0.4 at the 68% confidence level. Our derived value agrees with determinations from H II regions and with theoretical predictions from stellar yields with standard assumptions for the initial mass function. The amount of helium in stars determines how long they live and therefore how fast they will enrich the interstellar medium with fresh material.

1 Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA.
2 Tuorla Observatory, Piikkiö FIN-21500, Finland.
3 Centre for Astrophysics & Supercomputing, Swinburne University, Victoria 3122, Australia.
4 Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA.
*   To whom correspondence should be addressed. E-mail: raulj{at}physics.upenn.edu

Read the Full Text

To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)