Abstract
The chemical composition of the universe is rather simple. About 75% (by mass) of atomic matter is in the form of hydrogen, and almost all the rest is in the form of helium.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
Neutrons in atomic nuclei are stabilized by strong nuclear interactions.
- 2.
This number is easy to understand, considering that (i) there are 7 protons for each neutron (or 14 protons for 2 neutrons) and (ii) almost all neutrons end up in helium. For each helium nucleus (capturing 2 neutrons and two protons), 12 protons (hydrogen nuclei) are left free. Therefore, by mass, there is a 12:4 ratio of hydrogen to helium, which is precisely the 75% hydrogen, 25% helium prediction.
- 3.
The lithium abundance obtained by more accurate recent measurements is lower than predicted by about a factor of 3. The origin of this discrepancy is presently unclear; it is a subject of intense investigation.
- 4.
If the progenitor star has a mass between 8 and 20 Solar masses, the remnant left after core collapse is a super-dense neutron star. Core collapse in stars more massive that 20 Solar masses is expected to produce black holes.
- 5.
We emphasize that primordial nucleosynthesis is the only explanation we have for the abundances of helium and other light elements. This particularly applies to deuterium, which can only be destroyed in stars. And the amount of helium produced in all stars is only around one percent of the total amount observed in the universe.
- 6.
The physical principle behind the spin-up of a contracting cloud (and the ice-skater) is angular momentum conservation.
- 7.
Alternative forms of biochemistry have also been hypothesized. For example, life might be based on silicon and use ammonia as a solvent. Here we focus on Earth-like life.
Author information
Authors and Affiliations
Rights and permissions
Copyright information
© 2017 Springer International Publishing AG
About this chapter
Cite this chapter
Perlov, D., Vilenkin, A. (2017). Element Abundances. In: Cosmology for the Curious. Springer, Cham. https://doi.org/10.1007/978-3-319-57040-2_13
Download citation
DOI: https://doi.org/10.1007/978-3-319-57040-2_13
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-57038-9
Online ISBN: 978-3-319-57040-2
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)