Gunn-Peterson effect
In astronomical Spectroscopy, the effect Gunn-Peterson is a characteristic of the spectrum Quasar S of Redshift higher than 6 which is explained by the absorption of the radiation of the quasar by the hydrogen neutral (hydrogen atomic). The effect comes owing to the fact that the intergalactic hydrogen located on the line of sight absorbs the photons of the line Lyman alpha whose energy is shifted towards the red, the shift depend on the distance from the cloud from hydrogen.
The close quasars and the galaxies do not show such an absorption, indicating that the matter located between the galaxies at recent times is ionized. The spectra of the quasars of redshift higher than 6 show a hollow between the lines of hydrogen, up to a value of redshift from approximately 6. This lets suppose that the matter of very young the Univers was not completely ionized.
Following the results of WMAP I (2003), the time of Réionisation provided by the Gunn-Peterson effect appears to be in dissension with the estimates of Densité of column of the electrons obtained by WMAP. However, following the publication of the data of WMAP III in 2006, the two methods seem to give results a little less contradictory.
This effect was proposed by Gunn and Peterson in 1965 and was observed for the first time on the quasars discovered by the Sloan DIGITAL Sky Survey in 2001.
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