Astronomers use spectroscopy to study light from stars and planets. When light passes through a gas, certain wavelengths are absorbed by elements in the gas, producing an absorption spectrum with dark lines. When a gas emits light, it produces an emission spectrum with bright lines. How are spectral lines in a star's light useful to astronomers?
Answer
A
The absence of spectral lines means the star is not composed of any known elements.
B
The number of spectral lines in a star's spectrum determines the star's brightness.
C
The discrete wavelength of light a star emits helps astronomers predict the star's color.
D
The spectral lines in a star's light indicate the presence of specific elements in its atmosphere.
Explanation
Each element absorbs or emits light at particular wavelengths, creating a distinctive pattern of spectral lines. Astronomers compare the lines in starlight with known patterns to identify elements in the star’s atmosphere. Therefore, the correct choice is D: spectral lines indicate the presence of specific elements.
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