How you determine the temperature, composition, and motion of an object from its light spectrum?

Answer 1

Temperature is related to the overall distribution of light between the colors. Cooler things emit more light from the red or infrared part of the of the spectrum. The hotter something gets, the more blue and ultraviolet light it emits.

Composition can be determines from the fine bright and dark lines in a detailed spectrum. They are very specific wavelengths, or very small color ranges, where more or less light is emitted.

Motion toward or away from the observer can be determined by the shift in the positions on the above mentioned fine lines. Movement away from the observer makes the lines move toward the read end of the spectrum. This is how the expansion of the universe is measured.

Answer 2

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