Objects cannot move away from an observer faster than the speed of light in classical physics. According to Einstein's theory of relativity, the speed of light in a vacuum, denoted by 'c,' is an absolute speed limit. It means that no material object with mass can reach or exceed the speed of light.
However, when an object is moving away from an observer at speeds close to the speed of light, there is a phenomenon called redshift that occurs. Redshift refers to the observed shift of light towards longer wavelengths, which correspond to lower frequencies or redder colors.
The redshift occurs due to the relativistic Doppler effect. As an object moves away from an observer at high speeds, the light emitted by that object gets stretched or "stretched out" during its journey to the observer. This stretching of the light waves leads to an increase in their wavelength and a corresponding decrease in frequency. Consequently, the light is shifted towards the red end of the electromagnetic spectrum.
It is important to note that this redshift phenomenon applies to light and electromagnetic radiation. The object itself does not change color; rather, the color of the light it emits or reflects appears shifted towards the red end of the spectrum when observed from a distance.
In summary, objects moving away from an observer at speeds close to the speed of light experience a redshift phenomenon due to the stretching of light waves, resulting in a perceived shift towards longer wavelengths or redder colors. However, it is not possible for objects with mass to move away from an observer faster than the speed of light in classical physics.