Astrophysics (Index)About

Big Bang nucleosynthesis

(BBN, primordial nucleosynthesis)
(creation of atomic nuclei in the very early universe)

Big Bang nucleosynthesis (or primordial nucleosynthesis) is nucleosynthesis (the creation of atomic nuclei) occurring in the minutes immediately after the Big Bang, i.e., the first nucleosynthesis in the very early universe. In the study of cosmology, the effect of the extreme temperature immediately after the Big Bang along with known of the laws of physics is worked out, calculating the abundances of elements likely to have been produced. Today's observed abundances must be the result of this plus the effects of the later nucleosynthesis within stars and supernovae, and represent a constraint on theories of all this nucleosynthesis.

Theorized stable products of this very early nucleosynthesis are largely hydrogen-1 (i.e., with mass number 1) with some helium-4, along with far less deuterium, helium-3, and lithium-7. Following are the abundances theorized to be left over after the initial drop in temperature, which are termed relic abundances or primordial abundances:

Isotope (rough) mass fraction
H 0.75 (Xp)
He 0.25 (Yp)
2H aka D 10-4 (Dp)
3He 10-4
3H 10-6 (radioactive)
7Be 10-10 (radioactive)
7Li 10-10

The primordial radioactive isotopes would have long since disappeared, and any current abundance depends upon relatively recent nucleosynthesis. A more precise value of the primordial helium abundance is of current research interest in part because cosmological models relate the exact value to other quantities of interest. Recent determinations still vary, one being 0.2446.


(physics,cosmology,nucleosynthesis,Big Bang,early universe)
Further reading:
https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis
http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/bbnuc.html
https://www.astro.ucla.edu/~wright/BBNS.html
https://w.astro.berkeley.edu/~mwhite/darkmatter/bbn.html
http://faculty.tamuc.edu/cbertulani/ast/lectures/Lec12.pdf
https://physicsworld.com/a/testing-the-elements-of-the-big-bang/

Referenced by pages:
abundances
cosmic neutrino background (CNB)
deuterium (D)
early universe
helium (He)
hydrogen (H)
lithium (Li)
lithium burning
mass fraction
metallicity (Z)
missing baryon problem
neutralino
nucleosynthesis
Population III (Pop III)
radiation era
radioactivity
relic
stellar population

Index