What phenomenon allows astronomers to measure radial velocity by observing spectral line shifts?
Answer
Doppler shift of spectral lines
Measuring motion is a core task in astronomy, and this is divided into movement across the sky (proper motion) and movement toward or away from the observer (radial velocity). Radial velocity is determined through the analysis of the object's light spectrum. Specifically, if an object is moving toward the observer, its spectral lines will exhibit a shift due to the Doppler effect, known as blueshift, while movement away causes a redshift. This shift in the spectral lines directly quantifies the speed along the line of sight, which is vital for dynamic calculations like determining the masses in binary systems.
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