Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso

Z (Astrophysics)

  • Daniel Rouan
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1702-4


In astrophysics, Z is used to denote the mass fraction of all elements except hydrogen and helium in a star or other astronomical object. Those elements, considered as “heavy elements” and often called “metals” by astronomers, differ with respect to hydrogen and helium because their production implies processing by a star, either through nuclear reactions during the Main Sequence or giant phase or as a consequence of a supernova explosive event at the end of the star’s life. The abundance of these heavy elements is thus a very important indicator of the processing by stars in a galaxy.

In contrast, lower case z is used by astronomers to denote the redshift of a (typically) distant object moving away from the observer.

See Also


Mass Fraction Bioorganic Chemistry Nuclear Reaction Important Indicator Heavy Element 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.LESIAObservatoire Paris-Site de MeudonMeudonFrance