Lyman-alpha forest

As Lyman - α - forest / Lyman-alpha forest (also Lyα forest, in the jargon often called English Lyman -alpha forest ) are called clusters of sharp absorption lines in the spectrum of quasars. These lines are caused by the absorption of light by clouds of intergalactic gas on the line of sight to the quasar, mainly the Ly- α transition of neutral hydrogen. Since the passage of light takes place through these gas clouds at different redshifts ( different distances ), the Lyman-alpha forest closes in on the shorter wavelength side of the redshifted Ly- α emission line of the quasar.

As studies have shown, the number of these lines with the distance of the objects from which the astronomers ableiteten that the lines are not caused by the objects themselves, but originate from hydrogen clouds located between the objects and the earth. This can be derived from the number, distribution and thickness (width and opacity ) of the absorption lines to draw conclusions about the distribution and density of the clouds ( and turn it of galaxies ) pull in the universe. From this information, in turn, astronomers can deduce some properties of the entire universe, as the structure of the cosmos, the Hubble constant and the density distribution.