What does the term "redshift" signify in astronomy?

The term "redshift" in astronomy specifically refers to the phenomenon where light waves emitted from an object, such as a galaxy, are stretched as the object moves away from the observer. This stretching of the light waves causes them to shift towards the red end of the spectrum, which corresponds to longer wavelengths. Redshift is a crucial concept in understanding the expansion of the universe; as objects move away from us, their light waves elongate, indicating that they are moving further away.

This can be observed in the light from distant galaxies, which often exhibit significant redshift, providing evidence for the Big Bang and the ongoing expansion of the universe. By measuring the degree of redshift, astronomers can determine how fast an object is receding, which helps in studying cosmic structures and the dynamics of the universe.

In contrast, other concepts mentioned in the choices do not pertain to the definition of redshift. For instance, the bending of light waves typically relates to gravitational lensing or the effect of refraction, while brightness increases or decreases due to distance and motion are not directly tied to the wavelength changes described by redshift. Additionally, the color changes of stars due to temperature involve their thermal emission and are distinct from the Doppler effect related