When a vibrating object is moving blank an observer, the measured frequency of the vibrations will be lower than if the object and observer are both stationary. If the vibrating object is moving blank an observer, the measured frequency of the vibrations will be higher than the actual rate of vibration of the object. When a star is moving towards an observer on Earth, the light spectrum of the star will appear blank compared to the light spectrum of the sun, which is considered to be in Earth's frame of reference.
When a vibrating object is moving **away from** an observer, the measured frequency of the vibrations will be lower than if the object and observer are both stationary. This phenomenon is known as the Doppler effect, which occurs for waves, including sound and light, when there is relative motion between the source and the observer.
If the vibrating object is moving **towards** an observer, the measured frequency of the vibrations will be higher than the actual rate of vibration of the object. This is also due to the Doppler effect, where the waves are compressed, and the observer perceives a higher frequency as the source approaches.
When a star is moving towards an observer on Earth, the light spectrum of the star will appear **blueshifted** compared to the light spectrum of the sun, which is considered to be in Earth's frame of reference. Conversely, if the star is moving away, its spectrum would appear **redshifted**. "Blueshifted" means that the wavelengths of the light are shorter, and hence, the light is shifted towards the blue end of the spectrum. This happens because the motion towards us compresses the light waves, increasing their frequency.