Lyman Alpha Forest
As Lyman-α-Wald / Lyman-alpha forest (also Lyα forest , in the jargon often English Lyman-alpha forest ) accumulations are sharp absorption lines in the spectrum of quasar designated. These lines are created by the absorption of light in clouds of intergalactic gas on the line of sight to the quasar, mainly by the Ly-α transition of the neutral hydrogen . Since the passage of light through these gas clouds takes place at different redshifts (i.e. at different distances), the Lyman alpha forest joins the quasar's redshifted Ly α emission line on the shorter wavelength side .
As studies have shown, the number of these lines increases with the distance of the quasars, from which the astronomers deduced that the lines are not caused by the quasars themselves, but come from hydrogen clouds that are located between the quasars and the earth. This allows conclusions to be drawn about the distribution and density of clouds (and, from this, of galaxies) in the universe from the number, distribution and strength ( width and opacity ) of the absorption lines . From this information the astronomers can in turn derive some properties of the entire universe, such as the structure of the cosmos , the Hubble constant and the density distribution.
See also
Web links
- World of Physics: Of large walls and empty rooms - the architecture of the cosmos ( Memento from July 3, 2013 in the Internet Archive )