The spectra have the same shape so you can just look at what the wavelength shift is for one of the peaks or absorbtion lines.Ellio said:
The purpose of comparing spectra of distant galaxies is to gain a better understanding of the composition, structure, and evolution of these galaxies. By analyzing the light emitted from these galaxies, scientists can determine the elements present, their relative abundance, and the physical conditions of the galaxy.
Scientists use a technique called spectroscopy to compare the spectra of distant galaxies. This involves breaking down the light from the galaxy into its component wavelengths and analyzing the absorption and emission lines to identify the elements present and their properties.
The comparison of spectra can tell us about the redshift of a galaxy, which is a measure of how much the light from the galaxy has been stretched due to the expansion of the universe. This redshift can then be used to calculate the distance of the galaxy from Earth.
By comparing the spectra of distant galaxies, scientists can study the evolution of the universe over time. This can provide insights into the formation and growth of galaxies, the distribution of matter and energy in the universe, and the overall structure and history of the universe.
One of the main challenges is the redshift of the galaxy, which can cause the absorption and emission lines to shift to different wavelengths. This makes it difficult to accurately identify the elements present in the galaxy. Additionally, the distance and brightness of the galaxy can also affect the quality of the spectra obtained, making it challenging to compare different galaxies.