What phenomenon describes the shift in spectral lines from stars due to their relative motion?

The phenomenon that describes the shift in spectral lines from stars due to their relative motion is known as red shift. When a star or galaxy moves away from an observer, the light it emits undergoes an increase in wavelength, moving towards the red end of the spectrum. This shift provides important information about the motion of celestial objects and helps astronomers determine how fast they are receding from us.

Red shift is a critical concept in cosmology and is often used as evidence for the expanding universe, as distant galaxies are typically observed to be red-shifted, indicating that they are moving away. This observation is foundational in supporting the Big Bang theory and offers insight into the scale and structure of the universe.

The term "red shift" is often contrasted with "blue shift," which occurs when an object is moving towards an observer, leading to a decrease in wavelength and a shift towards the blue end of the spectrum. The Doppler effect is the underlying principle that explains both the red shift and blue shift, as it describes how waves change frequency or wavelength based on the movement of the source relative to an observer. However, in the context of spectral lines specifically resulting from stars moving away, red shift is the precise term. Gravitational lensing, on