what do the pattern of lines in a star's absorption spectrum represent?
The patterns of lines in a star's absorption spectrum represent the various wavelengths of light that are absorbed by the outer layers of the star's atmosphere. These lines are called absorption lines or dark lines.
To understand what these lines represent, we need to understand that stars emit light across a wide range of wavelengths. This light passes through the star's outer layers, which are composed of different elements like hydrogen, helium, and other heavier elements. The elements in the outer layers can absorb specific wavelengths of light, causing dark lines to appear in the spectrum.
The absorption spectrum is obtained by passing the star's emitted light through a spectrometer, which disperses the light into its different wavelengths, much like a prism. The resulting spectrum shows a continuum of light, interrupted by these dark absorption lines.
Each element has a specific set of energy levels at which its electrons can exist, and these energy levels correspond to specific wavelengths of light that can be absorbed. When light of the corresponding wavelengths passes through the outer layers of the star and encounters atoms or ions of specific elements, those atoms or ions absorb the light at these precise wavelengths, leaving dark lines at those positions in the spectrum.
The pattern of lines in a star's absorption spectrum provides valuable information about the composition of the star's outer layers. By comparing the observed lines with the known characteristics of different elements, scientists can determine which elements are present in the star and their relative abundances. This allows astronomers to study the chemical composition, temperature, and physical properties of stars, helping to deepen our understanding of stellar evolution and the universe as a whole.