recombination
(epoch of recombination)
(time when the universe's ionized hydrogen atoms neutralized)
In cosmology, recombination is a point in the history of the
universe around redshift 1090, at about 378k years after
the Big Bang, when electrons and protons
paired up to form neutral hydrogen atoms.
In this usage, the term is a misnomer because
this "recombination" is actually the first time
the electrons and protons were together.
This was the end of the photon epoch: when photons'
mean free path (between electrons and protons) was
short due to Compton scattering by electrons,
which had made space opaque. This lengthening of the photon
mean free path is known as the photon decoupling,
when one of the conditions of thermodynamic equilibrium
(photon interactions with matter the same energy distribution of photons
as are destroyed) was removed.
Recombination was the beginning of the dark age:
the universe was transparent but there were not yet stars.
The freed photons traveled freely,
many having no subsequent interaction with matter
(thus they were free streaming),
and now constitute the cosmic microwave background (CMB).
The term recombination has a more general meaning: the joining
of positive ions and electrons into neutral atoms. This also
occurs in other common situations, including many astronomical
circumstances, such as the interior of stars. A resulting emission
from such recombination is termed free-bound emission.
(Big Bang,cosmology,hydrogen,ionization,event,CMB,early universe)
Further reading:
https://en.wikipedia.org/wiki/Recombination_(cosmology)
https://astronomy.swin.edu.au/cosmos/e/epoch+of+recombination
http://star-www.st-and.ac.uk/~kdh1/ce/ce04c.pdf
https://people.ast.cam.ac.uk/~pettini/Intro%20Cosmology/Lecture09.pdf
Redshift | Parsecs /Distance | Lightyears /Lookback Years | | |
1090 | 4.29Gpc | 13.98Gly | | recombination |
|
Referenced by pages:
21-cm line
aurora
baryon acoustic oscillations (BAO)
CMB anisotropies
CMB polarization
continuum emission
cosmic microwave background (CMB)
cosmic neutrino background (CNB)
dark age
decoupling
diffusion damping
early universe
epoch of reionization (EOR)
free streaming
helium 1083 nm line
initial fluctuation spectrum
instability strip
Lyman alpha (Ly-α)
observable universe
radiation era
relic
Sachs-Wolfe effect (SWE)
Strömgren sphere
surface of last scattering
Index